Gricilli Lakes (LT)

The Gricilli Lakes (LT), also known as the Bishop's Lakes and called Triciglia by people from Sezze and Priverno, are a group of small bodies of water that surface on the Pontine plain, at the foot of the Lepini Mountains, in the territory of the municipality of Pontinia in the province of Latina, in a strip of reclaimed countryside that grazes the borders of Priverno and Sonnino. They are not lakes in the sense the word usually evokes: they have no spectacular outflow, they don't come from a dam, they don't occupy the crater of an extinct volcano. They are collapse sinkholes, that is, openings in the ground made by deep waters rising from the carbonate heart of the Lepini and which in some basins bring with them sulfur, carbon dioxide and dissolved salts. The result visible from the road is a succession of pools of different colors: three light blue, almost milky, with that unnatural tint that doesn't resemble any plain water, and one dark green of fresh water, all within a radius of a few hundred meters.

The area also includes Fontana di Muro, a very clear freshwater spring that gushes into a small basin, and borders the private equipped area of the Oasi di San Valentino, where the same sulfurous waters fill pools accessible for a fee. The two things must be kept distinct from the start, because confusion between the protected natural system and the private equipped land is behind almost all the misunderstandings of those who come here for the first time.

Where the Gricilli Lakes (LT) are and how you really get there

The geography of this corner of the plain explains everything else, and it's worth understanding before getting in the car. The system of small lakes occupies a narrow strip, a few kilometers long, between the course of the Uffente River on one side and the Rome-Naples via Formia railway line on the other, with the barrier of the Lepini Mountains closing the horizon toward the interior. Along the railway runs a service road, the Strada dei Gricilli, and that is the natural access route: from there you see the pools, from there you photograph them, from there you understand how they're arranged.

The reason the water is still here, in a plain that was drained entirely, is that at Gricilli the water didn't come from the sky but from below. It rose and still rises from the deep aquifer housed in the fractured carbonate rocks that continue the Lepini massif beneath the blanket of sediments of the plain. Against a spring pushing from the subsoil a drainage canal can do nothing: you can drain a marsh fed by rain and rivers, you can't drain a pressurized aquifer. This hydraulic irreducibility is the reason the Gricilli still exist while tens of thousands of hectares of marshes around have become fields of wheat and kiwi.

By car from Rome

The most direct route starts from the Grande Raccordo Anulare and takes Via Pontina toward Latina. You pass Latina, continue toward Pontinia, then aim for the signs for Priverno and for the abbey of Fossanova, which is the most visible landmark of the area and appears on the signs long before the name Gricilli. The Strada dei Gricilli branches off from that junction and runs parallel to the railway, among the fields. In ordinary conditions it's between 90 and 100 minutes from the ring road. On weekends in the good season the Pontina loads up with traffic heading to the coast and the time becomes hard to estimate, with slowdowns concentrated between Aprilia and Latina in the morning southbound and in the late afternoon northbound.

A second route exists, less traveled and often better, which arrives from the opposite side: A1 highway, Frosinone exit, descent toward Priverno through the Amaseno valley. The kilometers increase, the total time changes little and you avoid the Pontina entirely. Moreover the final stretch crosses a countryside of olive groves and arable fields that is worth the trip in itself. Those leaving from Naples or southern Lazio find this route entirely natural.

The last kilometer

Here it's best to be precise, because this is the point where most visits get complicated. The countryside around the small lakes is a mosaic of private farmland, and the network of farm roads branching off the Strada dei Gricilli leads nowhere for those who don't know the place. Satellite navigators, chasing the shortest route, regularly propose dirt tracks that end in front of a closed gate or inside a farmyard. The only rule that works is to stay on the paved road alongside the railway and use the viewpoints that open on the side of the lakes, without trying shortcuts.

By train

The reference station is Priverno-Fossanova, on the Rome-Naples via Formia railway line, served by the regional trains linking Roma Termini to southern Lazio and Campania. From the station to the area of the small lakes the distance is covered in a few minutes by car or in about 20 minutes by bicycle on flat road. There is no urban shuttle service and taxis at the station aren't always present: whoever arrives without their own vehicle risks being stuck. The best solution for those thinking without a car is to bring the bicycle on the train, allowed on the equipped cars of this line. From Priverno-Fossanova you can comfortably close in one morning a loop that touches the Cistercian abbey, the small lakes and the spring of Fontana di Muro. The only serious warning is shade, which is scarce along the road and in July makes the route tiring after 10:00 in the morning.

Parking

There is no equipped parking lot. Along the Strada dei Gricilli open spontaneous pull-offs and grassy widenings that on summer weekends fill up quickly, with cars left on the verge and passages made complicated for farm vehicles, which work here all year and need to enter and leave the fields. Leaving the car without obstructing access to the fields isn't an optional courtesy: it is exactly the reason why, over the years, several owners in the area have closed their passages to the public. Those who find the pull-off occupied would do better to continue and look for the next widening rather than inventing a creative arrangement.

What the Gricilli Lakes (LT) really are: sinkholes, not lakes

The word lake, applied to these bodies of water, is misleading. Whoever arrives imagining a wide surface to cross by boat is thrown: the largest measures a few tens of meters and is crossed by the eye in an instant. The substance of the place is something else, and it is geological.

These basins are sinkholes, that is, chasms produced by subsidence of the ground. The mechanism that technical studies reconstruct combines several factors acting at the same point: the progressive subsidence of the Pontine plain, that is, the slow lowering of the sediments that fill it, the presence at depth of fractured carbonate rocks that extend the Lepini massif beneath the plain, an active underground water circulation inside those fractures, and hydrothermal manifestations that rise along the faults carrying gases and salts to the surface. The specialist literature describes two distinct circuits coexisting in the same subsoil, a karst one of fresh waters and a hydrothermal one of mineralized waters, and attributes the genesis of the basins to a phenomenon of geothermal karst governed by tectonic dislocations still active in the Quaternary.

Translated into understandable terms: the water rising from below, aggressive because loaded with carbon dioxide, dissolves limestone at depth and creates cavities. When the vault of a cavity can no longer bear the weight of the sediments above, the ground collapses suddenly and a basin opens that fills with water. It's not a slow, imperceptible process like the erosion of a river, it's a sudden event, which those who live here have seen happen.

The proof that the process continues

In April 1991 the area recorded ground subsidence documented in studies of the sinking phenomena of the Pontine plain: lowerings of the ground that in some points stayed under a meter and in others approached two meters, accompanied by fractures with marked inclinations. That episode is the reason the Gricilli appear in the Italian technical literature on sinkholes as a reference case, and not as a scenic curiosity. The ground here still moves, and the look of the place seen today isn't the final one.

The sulfurous waters and the fresh waters

The particularity that makes this system rare is the coexistence, in a space of a few hectares, of chemically opposite waters. The sulfurous basins are fed by a deep circuit and contain sulfates, chlorides, high levels of dissolved carbon dioxide and sulfur compounds: they're strongly mineralized and strongly encrusting, leave whitish deposits on stones in prolonged contact and have the acrid smell of hydrogen sulfide, recognizable from a distance even before seeing the water. The opaque light blue color doesn't depend on a pigment but on the suspension of very fine mineral particles that scatter light.

Next to them, a few tens of meters away, other basins collect fresh water of very low salt content, clear and dark green. In the historical terminology of southern Lazio the waters of the first type are called albule, the same term used for the springs of Bagni di Tivoli. The coexistence of the two regimes at such close range is found in Lazio only in two other contexts: the plain of San Vittorino near Cotilia, in the Rieti area, and in part the Tivoli area with the system of the Acque Albule. Three places in the whole region.

A necessary clarification on access

The bodies of water of the Gricilli are largely on private land and fall inside a site protected at the European level. The banks are not equipped, there are no marked openings, no supervision, no declaration of bathing suitability. The inviting color authorizes no conclusion about being able to enter the water, and taking the water does not appear to be allowed. Those seeking a bath in the sulfurous waters of this system should turn to the private equipped area of the Oasi di San Valentino, which is a few hundred meters away and has carved its pools inside its own land, with paid entry and its own rules. Treating the natural basins like a free beach is the quickest way to get even the last remaining accesses closed.

The three groups of bodies of water: San Carlo, the Bishop's Lakes, Mazzocchio

Whoever walks the Strada dei Gricilli from north to south meets the system in three distinct stages, and knowing the sequence before leaving changes the quality of the visit: two of the three groups are easily lost.

Lake San Carlo

The first basin you meet arriving from the Priverno side is Lake San Carlo, isolated from the others and perfectly circular, with a diameter on the order of 80 meters. The round shape is the typical signature of collapse: when a deep cavity gives way, the resulting basin tends toward the circumference, because the subsidence propagates radially. Seen from the road it looks like any pond. Seen in an aerial photograph it becomes evident that it is a hole, not a natural depression shaped by surface water.

The group of the Bishop's Lakes

Going south you reach the main core, the one that properly bears the name Bishop's Lakes: four close bodies of water, three of them sulfurous and one fresh. The three sulfurous ones are recognized at first glance by the milky light blue, and in the local literature appear under the names Lago Bianco, Lago Verde and Lago Piccolo. The fourth, fresh water, is called Lago Nero. It's distinguished by the darker color and above all by its shape, which seen from above draws a fairly clear figure eight, a sign of two adjacent basins that collapsed at different moments and then merged.

The dimensions deserve a note of honesty, because the available sources don't match. The popular information sheets that have circulated for years report for the figure-eight basin a maximum length of around 150 meters and a depth of about 18 meters. The technical studies on the sinking phenomena of the Pontine plain collected in institutional settings describe instead sub-circular outlines with diameters between 120 and 130 meters and average depths between 10 and 15 meters. The two measures don't necessarily exclude each other, because one concerns the overall length of a bilobed body and the other the average diameter of the individual basins, but they remain estimates and should be taken as such. The figure on which all sources agree is the elevation: these basins sit at levels close to the sea, with bottoms that in some points go below zero altitude, which says a lot about the hydraulic condition of the whole Agro Pontino.

Lake Mazzocchio

Still farther south, in a position that makes it practically invisible from any road, is Lake Mazzocchio. It's surrounded by reeds several meters high and a eucalyptus wood planted in the reclamation era, and this double vegetation curtain works as a perfect screen: those passing by car don't see it at all, and many descriptions in circulation cite it without the writer ever having really seen it. It's fed by a canal that, past a pumping station, returns farther downstream to the Uffente River. Its character is different from the others: less a colored pool, more a real wetland, with the wildlife that a wetland entails.

A curiosity about the Gricilli Lakes (LT)

The most instructive curiosity concerns the number of names. A group of four pools and a few hectares of meadow has accumulated three popular names and two technical codes, and each of these labels tells a different piece of the place's story.

Gricilli is the most recent name: it indicates the agricultural locality and the road born with the 20th-century reclamation, and it's the one that appears on road maps and signs. Bishop's Lakes is the ancient name and refers to the ecclesiastical landholding of these lands, in an area where the diocese exercised for centuries rights over vast stretches of pasture and marsh. Triciglia, finally, is the name that came before all the others: it's the dialect place name that appears on no official map and survives only in the spoken use of Sezze and Priverno. Whoever asks an elderly local for directions using the map names risks a puzzled look. Whoever says Triciglia is understood on the first try and gets precise directions.

To the three names are added two codes. The first is IT6040003, the code under which the site appears in the European network of sites of community importance and as a special protection area. The second is number 50, by which the regional legislation of Lazio placed the area among the geosites of the hydrogeological system of the Lepini Mountains, within the framework of regional law number 29 of 1997 on protected natural areas. A place crossed in 10 minutes on foot bears five different designations, which is in itself a clue to how contested, used and studied it has been.

Fontana di Muro and the fresh water inside a sulfurous system

A short distance from the light blue basins is what for the people of the area is the dearest place of the whole system: Fontana di Muro, a freshwater spring that gushes into a small pool of remarkable clarity. The contrast with the milky opacity of the sulfurous pools a few hundred meters away is what strikes most: two waters born in the same subsoil, separated by a handkerchief of meadow, that seem to belong to two different worlds.

The name appearing in the oldest documents is Fontana Muro, without the preposition, and local tradition preserves the memory of a use that today sounds remote. During the seasonal transhumance, when flocks came down from mountain pastures toward the plain, the waters of this area were used to dress the animals' wounds and to whiten wool before processing. They are uses perfectly consistent with the chemistry of the place, because the antiseptic properties of sulfur have been known to pastoralism for millennia, and they place these bodies of water within a precise economic history: that of the sheep tracks linking the Apennines and the Lepini to the Pontine plain.

What you can do and what you can't

It's best to say it clearly, because the water's clarity generates the wrong expectations. There is no declaration of drinkability for this spring, there is no equipped collection point and the surrounding lands are largely private. Looking, photographing and sitting on a public margin without leaving a trace is one thing. Filling jerry cans, lighting fires or getting into the water is another, and the reports of local environmental groups concern precisely these practices. The fragility of the place is not rhetoric: the riparian vegetation of a handkerchief of land degrades within a few seasons if trampled by hundreds of people.

One thing nobody tells you about the Gricilli Lakes (LT)

That this place, in the perception of those arriving for the first time, practically doesn't exist as a place to visit. Not in the sense that it's unknown, but in the sense that the whole apparatus that usually turns a natural place into a destination is missing: there's no entrance, no panel explaining what you're looking at, no marked path, no information point, no restroom, no drinking fountain. You find yourself on a country road with colored basins of water on the side, and the visit consists of exactly that.

The practical consequence is that whoever organizes a whole day here without other stops goes home disappointed, and the disappointment is deserved: the sensible time to stay in front of the basins, for someone without binoculars and not a geologist, ranges from 20 minutes to an hour and a half. The Gricilli work as a stop within an itinerary, not as the sole destination of a trip from Rome. Whoever treats them as the main destination is making 100 kilometers for 20 minutes of looking.

The second thing: the season overturns the experience

The water that feeds this system comes from a deep circuit and keeps a substantially constant temperature all year round, on the order of 20 degrees Celsius. On the Pontine plain this means that in summer, with the air around 40 degrees, the pools are simply cool and convey no thermal sensation. In winter, instead, when the air temperature drops below 10 degrees, steam rises from the surfaces. The most extraordinary visual phenomenon this place can produce therefore happens in the month when nobody comes: a clear January morning, with frost on the plowed fields and smoke rising from the light blue pools against the profile of the Lepini.

The third thing: mosquitoes

No tourist description writes it, and it should be the first line of all. You are in a residual wetland in the heart of an irrigated plain, with reeds, standing water and wet meadows: the ideal combination for a population of dipterans that from sunset onward becomes the dominant variable of any plan. From June to September the evening hours require repellent, long sleeves and a minimum of organization, or the day ends sooner than planned.

The advice I give you for visiting the Gricilli Lakes (LT)

The advice is twofold and goes against the habits of most who pass through here. First: come outside the beach season, on a clear day between October and April. Second: build a day in which the small lakes are one stop among the four or five planned, not the only purpose of the trip.

The reasons for the first part are concrete. In winter and in the mid-seasons the air is transparent and the barrier of the Lepini stands out sharp in the background, while in the summer haze of the Pontine plain the profile of the mountains evaporates into a gray mass. Mosquitoes, which from June to September affect every stop, practically disappear in these seasons. The low vegetation lets you see the water, which in summer stays hidden behind reeds over two meters high. And traffic along the Strada dei Gricilli is reduced to a few tractors, with the possibility of stopping where needed without looking for a spot for the car.

The reasons for the second part were explained just above: the visit time for the basins is short by nature. Whoever planned the day on a single stop finds themselves at noon with six hours to fill in a countryside without services.

The itinerary that works

Leave Rome early, without dawdling, because the Pontina rewards those who travel it before 8:00. First stop at the abbey of Fossanova, one of the best-preserved Cistercian complexes in Italy, a few minutes from the small lakes, where an hour and a half passes without noticing. Second stop along the Strada dei Gricilli, stopping at the viewpoints over the basins of the Bishop's group and then at the spring of Fontana di Muro: 40 minutes to an hour, more if you bring binoculars. Third stop, lunch: here the choice depends on the program, because the Gricilli countryside offers no dining and the reasonable options are a packed lunch, with a serious cooler bag in summer, or a trattoria in Priverno or Sezze. Afternoon up in the hills, going up toward one of the villages of the Lepini Mountains: Sezze and Priverno are the closest, but with half an hour more you reach Sermoneta, Bassiano, Norma or Cori. The contrast between a plain at sea level and towns perched on rock at 500 meters elevation is the real spectacle of this province, and the Gricilli are its natural gateway.

What to bring

Closed shoes with a sole that grips: the grassy edges of the basins are irregular and in some places yielding. Binoculars, which in this context are worth more than any other item: the aquatic fauna of a protected site is observed from a distance, and without optics you see very little. Drinking water brought from home, because there are no fountains here. Mosquito repellent from May to October. A hat, since shade along the road is almost absent. A bag to take your own trash away, which in a site of a few tens of hectares with recurring reports of dumping is not a symbolic detail.

Protected nature: habitats, species and the code IT6040003

The portion of territory that includes the Gricilli and the spring of Fontana di Muro is recognized as a site of community importance and as a special protection area, with the code IT6040003. It is the only area of the municipality of Pontinia to enjoy this recognition, and the perimeter grazes the neighboring territories toward Priverno and Sonnino.

The recognized habitats

The documentation accompanying the protection lists four types of habitat of community interest: Mediterranean tall-herb wet meadows, oligo-mesotrophic calcareous waters with Chara vegetation, natural eutrophic lakes and oligotrophic waters of very low mineral content. Put understandably, it goes like this: in a space of a few hectares coexist aquatic environments chemically at opposite poles, from waters very rich in salts to those almost devoid of minerals, with the whole intermediate range. This coexistence is precisely what makes the site rare, and explains why its protection is justified not by the beauty of the landscape but by its chemical and biological composition.

The species

Among the species cited in the protection sheets are the kingfisher, the European pond turtle and two freshwater fish of Italian fauna, the Italian roach and the spined loach. On the plant side the reports concern water lilies, ferns, wild orchids and the specialized marsh formations that grow only where water remains all year. It's not the list of a great national park, and that is exactly the point: these are small, isolated populations, survivors in a handkerchief of land surrounded by intensive agriculture, and for this reason fragile in a way wholly out of proportion to their extent. A single season of heavy disturbance can do to a local population what in a park of 20,000 hectares would take decades.

Protection on paper more than on the ground

The European recognition has existed for years and for just as many years local observers report that it hasn't translated into operational management. The proposal to establish a natural monument has been put forward repeatedly, supported by environmental groups of Pontinia, without reaching completion. In local chronicles the same items always recur: trash abandoned along the banks, alterations to riparian vegetation, fires lit near the spring, unregulated access, vehicles passing where they shouldn't. This also explains why part of the surrounding land has been progressively fenced by the owners: in the absence of public regulation, private closure remains the only tool available to those who own the land.

Whoever visits this place with care contributes to a concrete cause, and it's not a formula of courtesy. Every correct behavior makes it less likely that yet another gate will be closed. Every incorrect behavior speeds the closing. In a site of this size the relationship between visitors and environment is direct and immediate.

Another well-known fact, yet rarely mentioned

The well-known fact is that the Gricilli represent one of the last fragments of pre-reclamation landscape left in the Agro Pontino. You read it everywhere and it's repeated mechanically. What almost nobody adds is the numerical comparison, and the comparison changes the perception of the place.

Before the 1930s the Pontine plain was a marshy expanse of tens of thousands of hectares: a continuous system of marshes, reed beds, lestre and hygrophilous woods that rose from the coast up to the slopes of the Lepini, crossed by watercourses that couldn't reach the sea and by a belt of dunes that blocked the outflow. The integral reclamation transformed all this in a few years into an agricultural territory drained by hundreds of kilometers of canals and kept dry by pumping stations that still work today, without which a large part of the Agro would go back underwater within seasons. Of that original environment three significant testimonies remain: the Gricilli, the wetlands inside the Circeo National Park with the Pantanello area, and the spring system of Ninfa. From tens of thousands of hectares to a few tens: this is the real ratio, and it is the reason a handful of pools deserves attention.

The second little-cited fact

The geochemical rarity of this system is recognized among specialists and almost never mentioned elsewhere. The coexistence, in such a restricted space, of strongly mineralized sulfurous waters and fresh waters of very low salt content is found in Lazio only in two other contexts: the plain of San Vittorino near Cotilia, in the Rieti area, and in part the Tivoli area with the system of the Acque Albule. Three places in the whole region, and the Gricilli are the only one of the three that still presents itself in a substantially agricultural guise, without establishments, without building and without infrastructure. The value of this place isn't postcard, it's chemical, and becomes visible in the palette of colors you observe from the road, with light blue pools and green pools 50 meters from each other.

The third fact: the link with Ninfa

The Garden of Ninfa, about 30 kilometers away along the same edge of the Lepini, comes from the same hydrogeological phenomenon as the Gricilli: waters of the Lepini that resurface at the base of the massif after an underground course inside carbonate rocks. The difference is in the destiny: at Ninfa those waters were channeled, cultivated and transformed into one of the best-known gardens in Europe, while at the Gricilli they stayed where they were, in collapse basins in the middle of the fields. Visiting the two places on the same day means seeing two opposite outcomes of the same geological cause, one monumental and one raw, and there's no better way to understand how the eastern margin of the Pontine plain works.

The right photo to take at the Gricilli Lakes (LT)

The wrong photograph, the one everyone takes home, is the shot from above the road with the pool in the center and the fields around: it comes out flat, the color of the water is lost and the result looks like any irrigation pond. The subject of this place is only one, the color, and has to be built with some technical care.

The time

The milky light blue of the sulfurous waters is a color of raking light. It lights up in the first hour after dawn and in the hour before sunset, while the overhead noon sun whitens and flattens it until it looks like a dirty gray. Early morning adds a decisive advantage: the surface is still and gives back the reflection of the Lepini barrier, doubling the image.

The angle

You have to crouch down to bring the camera or phone a few centimeters from the surface of the water, and compose the frame in three horizontal bands: the light blue water in the foreground, the green band of meadow and reeds in the middle, the profile of the mountains above. It's an elementary composition that always works here, because it exploits the color contrast that constitutes the visual identity of the place. From eye height, standing, the same subject loses half its force.

The filter

A polarizing filter radically changes the result. By reducing specular reflections on the surface, it lets the mineral suspension that gives the water its color emerge and returns a saturation that the eye perceives and that the sensor alone doesn't record. On a sulfurous pool the difference between a shot with and without polarizer is the difference between a photograph and a memo.

The photo almost nobody takes home

The steam rising from the sulfurous basins on a cold winter morning, backlit, with the low sun crossing the fog and frost on the plowed fields around. You need a clear January day, a departure from Rome before dawn and the willingness to stand in the cold for a good hour. In return you get an image that resembles no other photograph of the Pontine plain, and that none of the summer visitors will ever see in person.

Some important events that happened here in history

Four pools and a few hectares of meadow seem to have no history, and yet the story of this corner coincides with that of the whole plain. It's best to line it up: every step has left a sign still readable on the ground.

The very long age of the marsh

For centuries this strip of plain was land of marshes and malaria, the territory that the popes tried repeatedly to drain without lasting success. Documented interventions followed one another from the Middle Ages to the modern age, with canals dug, reopened and then closed again by silting. In that context the Gricilli were not an anomaly but normality: standing water, reed beds, seasonal pasture. The ecclesiastical ownership of the lands, at the origin of the name Bishop's Lakes, belongs to this very long phase, during which human presence was tied to sheep-farming and transhumance more than to settled agriculture.

The integral reclamation of the 1930s

The reclamation is the event that redrew the landscape in which the small lakes lie. In a few years the marsh was drained by a network of drainage canals and collectors, the new towns of the plain arose and thousands of settlers arrived from Veneto and Friuli, whose accent and surnames are still recognizable today in the towns of the Agro. In the middle of that decade Pontinia was also founded, the municipality that administers the Gricilli today, born as a service center for the newly redistributed countryside. For this corner of territory the consequence was paradoxical: the water rising from the subsoil couldn't be drained, and so a fragment of the old landscape survived precisely thanks to its own hydraulic irreducibility. The Gricilli still exist because the reclamation didn't manage to drain them.

1970 and the end of malaria

1970 is the year in which malaria is officially eradicated from Italian territory. For the Agro Pontino it was the closing of a chapter 2,000 years long, and for the Gricilli the moment when the pools stopped being perceived as a health threat and began to be seen as a resource. Recreational use of the sulfurous waters, with the first informal baths and then the first forms of organized management on the neighboring private lands, belongs to the following decades.

April 1991

In spring 1991 the ground gave way again, and the episode entered the specialist literature on the subsidence of the Pontine plain: the lowerings measured ranged from a few tens of centimeters up to values close to two meters, with inclined fractures in the surrounding fields. It's the episode that more than any other shows how these basins are not an inert remnant of the past, but the visible result of a geological process still under way. A sinkhole, in this plain, is not a filed-away event.

The European recognition and the geosite

The perimeter that includes the basins and the spring appears in the European network with the code IT6040003, both as a site of community importance and as a special protection area. On the regional side, Lazio law number 29 of 1997 on protected natural areas led to the inclusion of the area in the list of geosites tied to the Lepini hydrogeological system, where it bears the number 50. Around these acts a proposal to establish a natural monument has developed over the years, supported by local environmental groups, that so far has not reached the finish line.

September 27, 2020

On the afternoon of September 27, 2020 a fire destroyed the restaurant structure of the San Valentino equipped area, on Via dei Gricilli in the territory of Pontinia right by the border with Priverno. Firefighters worked a long time on site and no injuries were recorded, because the venue was not in operation at that moment. According to the reconstruction reported then by local newspapers, the trigger was supposedly a lightning bolt, which fell during the storm hovering over the area that afternoon. The episode concerns the neighboring private land more than the natural basins, but it's worth keeping in mind: the services of this area have known interruptions and reopenings, and no one can take them for granted.

Who passed through the Gricilli Lakes (LT)

Whoever expects a list of famous names will be disappointed: the available literature on this place records no famous figures. The value of the place is not worldly. The people who really crossed it leaving a mark belong to other categories, and telling about them is more useful than any anecdote.

The transhumance shepherds

The first visitors preserved by local memory are the shepherds who came down from mountain pastures toward the plain along the sheep tracks, and who used these waters to dress the animals' wounds and to whiten wool. A use that ties these bodies of water to an economy lasting centuries, and explains why an apparently marginal place was perfectly known to those who worked the territory long before it appeared on any tourist map.

The reclamation settlers

The Veneto and Friuli families who arrived in the 1930s to populate the new towns of the Agro Pontino are the protagonists of the most radical transformation this plain has known. Their descendants live today in Pontinia and the nearby towns, and for the most part they are the regular visitors to the small lakes: those who say Triciglia, who know every pull-off and who know which way to look to see the water without climbing any embankment.

The geologists

Among those who have spent more hours here than anyone are the researchers who studied the subsidence phenomena of the Pontine plain. The Bishop's Lakes appear in the Italian technical literature on sinkholes with measurements, sections and reconstructions of the deep water circuits. Without that work this place would be just a group of colored pools in the middle of fields. Thanks to that work we know why they're colored and how they formed.

The environmentalists of Pontinia

The last category is that of the local groups who over the years have documented the state of the site, reported abuses and supported the natural monument proposal. The European recognition this area carries did not come on its own: it's the result of pressure from below lasting decades, led by people who live a few kilometers away and who gained nothing from their work except the survival of the place.

When to go to the Gricilli Lakes (LT) and when to avoid them

Season counts here more than in any other place in the province, and the ranking is counterintuitive.

From October to April you find the best condition by far. The air is clear and the Lepini stand out sharp, mosquitoes disappear, the low vegetation lets you see the water, the road is almost deserted. January adds the phenomenon of steam rising from the basins on cold, clear mornings, which remains the most memorable image this place produces. The limit is the ground: after days of rain the grassy margins become muddy and the dirt pull-offs flood.

May and June are a good compromise, with wild orchids in bloom, bird activity at its peak and heat still manageable. The second half of September brings back similar conditions. Mosquitoes begin to make themselves felt in the evening.

July and August are the months to avoid, and the reasons add up: haze that erases the profile of the mountains, tall reeds that screen the water, abundant mosquitoes, intense heat on a plain with no shade, occupied pull-offs. Whoever has no alternative should come at dawn and leave by 9:00 in the morning.

What's around the Gricilli Lakes (LT)

The abbey of Fossanova and the villages of the Lepini

The Cistercian abbey of Fossanova, a few minutes by car, is the stop that completes the day better than any other. Going up toward the interior you meet Priverno, with its museums, and Sezze, overlooking the plain from a natural terrace. Farther north the Lepini Mountains Natural Park lines up Sermoneta with the Caetani castle, Bassiano with its walls and ham tradition, Norma hanging over the void and Cori with the temple of Hercules. On the opposite side Sonnino closes the hill belt toward the sea.

Water and gardens

The Garden of Ninfa comes from the same hydrogeological mechanism and represents its cultivated version: access is regulated by openings on set dates and by reservation, and has to be organized in advance. Lake Giulianello, at the northern end of the Lepini, offers a useful comparison with a basin of a different nature.

The sea and the coastal wetlands

The coast is reached in a good half hour. Terracina with the temple of Jupiter Anxur, the Torre Paola beach beneath the promontory, the Bufalara in the Sabaudia pinewood, San Felice Circeo and the Circeo National Park with the coastal lakes, among them Lake Fogliano. Farther north the Lido di Latina and the Rio Martino seafront. Toward the south Sperlonga. Those who want to understand the story of the reclamation find in Latina the Pontine Land Museum.

The accessible sulfurous waters

For a bath in the waters of this system the only equipped reference in the area is the Oasi di San Valentino, private land with paid entry. On the front of real establishments the historical reference of Lazio remains that of the Acque Albule at Bagni di Tivoli, which share the sulfurous chemistry with the Gricilli and nothing of the surrounding countryside.

Quick questions about the Gricilli Lakes (LT)

Can you swim in the Gricilli Lakes?

The basins visible from the Strada dei Gricilli are part of a site protected at the European level and sit largely on private land. There is no declaration of bathing suitability, and there are no equipped banks or supervision. The pools accessible in a regulated way are those inside the private land of the Oasi di San Valentino.

Can you collect the spring water?

It does not appear to be allowed and there is no equipped collection point. None of the waters of this system is declared potable.

Do you pay to see the lakes?

No: the road alongside them is public. You pay only to enter the neighboring equipped private land.

Why is the water light blue?

Because of the suspension of very fine mineral particles tied to the sulfur and salt content of the deep waters that feed those basins. The freshwater pools, lacking that load, appear dark green.

How much time does the visit take?

From 20 minutes to an hour and a half, depending on the number of stops and whether you have binoculars. It's best to fit them into a broader itinerary.

Can you get there without a car?

By train you get off at Priverno-Fossanova on the Rome-Naples via Formia line, but from the station a transfer is still needed: taxi, a ride or a bicycle. There is no dedicated public connection.

Is it suitable for children?

The walk along the road is easy and flat, but the margins of the basins are irregular, the water is deep and opaque and there are no barriers: supervision must be constant.

Is there a bar or refreshment point?

There are no services along the road of the small lakes. The nearest dining is in the towns of Priverno, Sezze and Pontinia, besides whatever may be active inside the neighboring private land.

What's the difference between the Gricilli Lakes and Fontana di Muro?

Fontana di Muro is the very clear freshwater spring found inside the same protected area. The Gricilli Lakes are the set of collapse basins, mostly sulfurous, that surround it. Same hydrogeological system, opposite chemistry and color.

The Gricilli Lakes should be taken for what they are: a geosite in the middle of fields, extraordinary for those who understand what they're looking at and modest for those who expect a lake. Whoever arrives with this awareness, on a clear cold-season morning and with time to go up afterward toward the hill villages, takes home one of the least predictable days of southern Lazio. Whoever arrives on Ferragosto hoping for a dip will find reeds, mosquitoes and a private property sign.

Frequently asked questions about the Gricilli Lakes (LT)

Can you swim in the Gricilli Lakes?

The basins of the Gricilli Lakes visible from the Strada dei Gricilli are part of a site protected at the European level and sit largely on private land: there is no declaration of bathing suitability, and there are no equipped banks or supervision. The pools accessible in a regulated way are those inside the Oasi di San Valentino.

What are the Gricilli Lakes really?

The Gricilli Lakes are not lakes in the proper sense but sinkholes, that is, chasms produced by subsidence of the ground. The largest of the basins measures a few tens of meters, much less than the word lake makes you imagine if you arrive thinking of a navigable surface.

Where are the Gricilli Lakes?

The Gricilli Lakes occupy a narrow strip a few kilometers long between the course of the Uffente River and the Rome-Naples via Formia railway line, with the barrier of the Lepini Mountains closing the horizon toward the interior, in the province of Latina.

When is the best time to visit the Gricilli Lakes?

From October to April you find the best condition for the Gricilli Lakes: the air is clear and the Lepini stand out sharp, mosquitoes disappear and the low vegetation lets you see the water. January adds the phenomenon of steam rising from the basins on cold, clear mornings.

Are there marked trails and information panels at the Gricilli Lakes?

No, at the Gricilli Lakes the whole apparatus that usually turns a natural place into an equipped destination is missing: there's no entrance, no panel explaining what you're looking at and no marked path, even though the place isn't unknown in the area.

Are the Gricilli Lakes a protected area?

Yes, the portion of territory that includes the Gricilli and the spring of Fontana di Muro is recognized as a site of community importance and as a special protection area, with the code IT6040003, the only area of the municipality of Pontinia to enjoy this recognition.

What is there to visit near the Gricilli Lakes?

Near the Gricilli Lakes, a few minutes by car, is the Cistercian abbey of Fossanova, which rounds out the day well. Going up toward the interior you meet Priverno and Sezze, and farther north the Lepini Mountains Natural Park with Sermoneta and its Caetani castle.

Article written by the editorial team of TourLeaderPro, contact them for Private/Corporate/V.I.P. Tours and Experiences. For an organized day among the Gricilli lakes, the abbey of Fossanova and the villages of the Lepini Mountains, with a licensed tour leader, start from the TourLeaderPro contact page. Tour operators who build itineraries in southern Lazio and the Agro Pontino find the consulting service in the section dedicated to tour operators.

Planning a trip to Rome? The English guides for visiting the city are on ItalyPlanner.com. For those thinking in terms of days outside the city there's the guide to the best day trips from Rome, while those looking for water and nature without beach establishments will also find useful the guide to the free beaches in Italy.