The Lake of Vouliagmeni
Complex of Karst Caves
Max Depth: 127m | Average Temp: 27°C
On the southern edge of Ymittos, a few meters from the eastern shores of the bay of Vouliagmeni, one of the world’s most beautiful and unique karst systems emerge.
Lake Vouliagmeni is a multi-dimensional geological phenomenon separated from the deep blue waters of the Saronic Gulf by a narrow strip of limestone rock.
The creation of this magnificent lake dates back 2,000 years ago or even later, during the early Christian times, with the collapse of the roof of a vast underground cave due to tectonic movements and the Cretaceous erosion of the limestone in the area.
All the data and subsequent geological studies carried out up to the present day converge on this. That explains the lack of historical evidence from Strabo and Pausanias and the later Stephanos Byzantius, who have given descriptions of the wider area in their time without mentioning the existence of such a doline.
Scientific Projects
The first attempts to explore the lake are said to have been started by the German conquerors in the 1940s during the years of occupation, but their findings have never been known.
In 1988, the Greek Ministry of Culture’s Department of Palaeoanthropology and Speleology took the first tentative steps towards the underwater exploration of the cave and immediately realized the difficulties and peculiarities of this project.
Several issues arise, such as the fact that the cave extends under the first building blocks of the city, the direction it takes regarding the residential area, its immense length, and its unknown depth leads the department to make immediate and crucial decisions.
In 1989, it invited some leading names of the time in exploratory speleology and geology to form a multinational scientific research team to carry out such a challenging task.
The team leaders from each country were Jean-Jacques Bolanz, Patrick Deriaz (Switzerland), Luigi Casati (Italy), Mare Douchet (France), Vassilis Giannopoulos (Dr. Geology, Paleoanthropology Speleology Ephorate, Greece), and Christos Agouridis (Archaeologist, Paleoanthropology Speleology Ephorate, Greece).
With these distinguished explorers at the core, but also many others supporting this effort, systematic research started, which lasted for eight exploration periods in 1989, 1991, 1992, 1992, 1993, 1995, 1996, 1997, and was completed in 2005 with the overall mapping up to that time, which gave the central axis of the cave and their conclusions.
During these years, it quickly became apparent, as recently as 1991, that the cave and the wider area were of enormous scientific interest. Thus, parallel with the underwater exploration, the literature search, the study of the flooded chamber’s morphology, geology, and tectonics, and the area where this complex geological phenomenon develops began.
Studies on this karstic system’s cave formation and hydrology complete the scientific approach and offer valuable conclusions.
According to Dr. Vassilis Giannopoulos, the Vouliagmeni dolina, the so far explored cave, the cave-basement “Germaniko,” the other four sinkholes that have been discovered in the nearby area, and probably the Karstic cave (the well-known “Well”) that exists in the 2nd Limanaki belong to the same Karstic complex, which has been created during the glacial period.
“The rocks in the area are limestone. The limestone favors cave formations through the physical and chemical erosion of water. The surface rocks gradually sank and formed a series of five sinkholes, i.e., visible from aerial photographs. Beneath them, the water continues to erode the limestone rock, opening up the chambers and galleries that form a labyrinthine system. We do not have a single cave, but a whole system of caves with the main direction to the north”, says Dr. Vassilis Giannopoulos.
During the last exploratory expedition in 2005, Luigi Casati found a stalactite at a depth of 105 m., about 5 m. long and 1.5 m. in diameter at a depth of 728 m. from the cave’s entrance, offering new data to scientists in their research on the formation and formation of the Mediterranean basin.
The Municipality of Vouliagmeni has been a great supporter of this project all these years and a warm supporter of this project, covering the accommodation and the operating costs of most of the expedition.
With the end of the multinational expeditions in the 2000s, members of caving clubs and groups of private cavers continued the systematic exploration of the cave. New passages and information about the cave’s structure came to light, and this day is constantly being revealed.
The underwater caves
There are three distinct caves on the lake’s perimeter, which can be visited. These are the “Parking”, “Luica” and the Main Cave.
The Parking & Luica Caves
On the west side of the lake, we find the Parking Cave located just below the outdoor parking area of the business on the coastal road.
Its maximum depth reaches 25m, and it is a large cave with a total length of about 100m.
Very close to the right and east of the main cave is the Luica Cave, named after the great Italian caver and explorer Luigi Casati, who discovered it during one of the first exploration periods of the International Expedition.
The average depth of the cave is 35m, and the maximum depth reaches 50m through a small siphon on the northeastern side of the chamber.
The light coming in from the cave’s entrance creates unique reflections, and the excellent visibility that always prevails inside the cave makes diving into it a memorable experience.
The Main Cave
In the northern part of the lake and especially at the entrance to the central cave, a small creek of limestone rocks measuring approximately 10 x 15m has formed on the surface because of the detachment and sedimentation of these materials.
To reach the main hall, one has to enter a first room where there is a large amount of sunlight and at a depth of 33m. to pass through the so-called “Window” measuring approximately 3 x 1.5m. which will lead one to a vast “tank” of water with a volume of up to 2,000,000 m3.
At this juncture, we are at a 40m depth in the first chamber, where the ceiling reaches 15m. and the depth reaches 70m.
Here the divers can move through the cave by following the two main routes, A & B, which pass through the second room that reaches a depth of 105m and a ceiling of 65m, ending up in the third and last room where the nature created a great depression and have divided this room into smaller ones with several corridors connecting them.
Route A, located to the right of the “window” and east of the cave, is the one which, in a side route of about 100m, leads to the depth of 100m. There, in a well-hidden opening behind a pile of precipices, we are led to the deepest part of the cave to date, which reaches 127m deep.
In contrast, route B is on the cave’s west side and to the window’s left. The team of Swiss explorers set it up and ran a 730m long route.
A main guideline installed by the SP.EL.E.O. in 2009 runs through the cave and leads faster to the Third Chamber.
The main hall is about 650m long, and its width ranges from 60 – 150m depending on the penetration point.
The cave’s ceiling in the first 150m of the route obliges one to move at 65m depth, while in most of the cave, the diving depth is 90 – 105m.
The water temperature is ideal for the great depths required to move and the following long decompression.
At a depth of 40m, the water temperature is a constant 27 degrees, and as we dive deeper, it increases, reaching a maximum of 29 degrees Celsius.
According to Dr. Giannopoulos, the most reasonable version of this phenomenon is the cave’s connection with the Aegean volcanic arc and, more specifically, with the section Sousaki – Aegina – Methana.
With the total number of explored routes to date amounting to 4.2 km. in a 933 m penetration length from the cave’s entrance and with a depth of up to 130 m, the main hall is considered one of the largest submerged halls in Europe.
The lake of Vouliagmeni today
The lake is 260 meters long and 145 meters wide in an ellipsoidal cavity. Although the area has been evolving geologically over the last 70 years, and the morphological changes have occurred through precipitation observed in aerial photographs from different periods, its general shape and image remain the same.
Less well-known and with no right of access to the general public is a second smaller lake located on the south side of the doline. It has remained known as “Lake Zolotas” since it often swum there throughout the year and was a favorite destination of the great academic, prime minister, and longest-serving governor of the Bank of Greece, Xenophon Zolotas.
Its diameter is about 20 meters, with its bottom sloping downwards to the vertical wall it is adjacent to, and its depth reaches 17 meters.
Due to the morphology of the bottom, scientists speculate that at this point, there could be an entrance and a continuation of a karst system, which has been closed by landslides and the accumulation of sediments from the surrounding hills.
Lake Vouliagmeni is the center of a rare ecosystem of outstanding natural beauty and multifaceted importance, part of the European ecological network Natura 2000.
It has been characterized as a Site of Special Natural Beauty by the Ministry of Culture, and in its waters live unique organisms, among which a species of sea anemone Paranemonia Vouliagmeniensis, the shellfish Cerastoderma Glaucum (Brackish Cockle), which acts as the living filter of the lake, as well as a large colony of Garra Rufa fish.
Its brackish waters are characterized by their curative properties. Its bottom consists of a muddy substrate rich in sulfur compounds, and its waters have a high content of minerals and trace elements.
Since 1992 the company “Thermal Loutra Vouliagmenis – Tourist Enterprises SA” has undertaken the commercial exploitation of the spa, allowing entry for a fee, while having created modern catering facilities and social events.
Accidents
In the ’80s and ’90s the lake of Vouliagmeni, with its warm waters, the ease of access, and the mystery it hid, made it a very attractive destination for many divers, but also for the first stages of their training.
The lack of training in cave diving, the absence of specialized equipment for roof diving, human errors, and omissions in safety rules led to a series of accidents that resulted in the loss of human lives.
Consequently, diving in the caves of the lake is now allowed after obtaining a permit from the management company and under the supervision of an affiliated cave diving instructor.
Expedition Timeline & Credits
Our team visited Lake Vouliagmeni during three different periods to produce audiovisual material of this unique karstic system:
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July 24, 2022: In collaboration with the Addicted2h20 diving team, we performed a penetration into the first chamber of the cave, reaching a maximum depth of 70m, with a minimum ceiling height of 15m.
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December 17-18, 2022: We returned to explore all three accessible underwater caves—Parking, Luica, and the Main Cave—focusing exclusively on capturing high-quality photographic material.
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April 14, 2024: In collaboration with the Up Stories team, we captured aerial and underwater footage to create a documentary film presenting the lake’s history to the general public.
The Diving Team: Akis Seisidis, Giorgos Toumpaniaris, Errikos Kranidiotis, Christos Michail, Nikolas Margaritis, and Andreas Andrikopoulos.
Text editor and archive research: Andreas Andrikopoulos
Photo: Nikolas Margaritis
Acknowledgments
We would like to extend our warmest thanks to Giorgos Vandoros, Cave and Technical Diving Instructor, who serves as the Safety Officer and Guided Diving Supervisor at Lake Vouliagmeni.
His years of dedication to exploring the lake and discovering new passages, combined with his unparalleled knowledge of the cave system, provide a unique blend of safety and world-class diving experience.
Sources
Yiannopoulos, V., 2000. A contribution to the study of contemporary and paleo-environments of the most significant caves of the Greek peninsula, Ph.D. Thesis, Athens, 429 pp.
Giorgos Vandoros, Cave Diving Instructor Trainer, Diving Instructor for the caves of Lake Vouliagmeni.
Vithos – December 1995
Free & Scuba Diving No89 – December 1996
Explore Nature No9 – December 2008
Greek Diver No.
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Greek