Czech scientists in Albania discover world’s largest underground thermal lake

Within the valleys of the mountainous borderlands between Greece and Albania, Czech scientists have for several years been exploring the complex situation underground. In the Vromoner region, on the Albanian side of the border, they came across an extensive system of caves back in 2021, which they have since been mapping in detail. The system contains many heated springs that release high columns of steam, and tracking a source of the steam led them to find an abyss over one hundred metres deep, which they named Atmos.

At the bottom of that abyss, the team have now confirmed the discovery of the world’s largest underground thermal lake to date. With a length of 138m, a width of 42m and a circumference of 345m, it can hold 8,335m3 of hot water. For a Czech comparison, the size of the lake’s chamber is three times larger than the main hall of the National Theatre in Prague.

Mapping the cave system and discovering the lake required technical equipment, which was made possible by the Neuron Foundation. The Czech scientific-funding organisation provided the expedition with almost a million crowns, donated by private benefactors, and now the underground Albanian lake has been named Neuron, in the foundation’s honour.

Richard Bouda, a photographer and speleologist, describes how the discovery was made:

“During the initial exploration, we created a basic map using the equipment we had. We knew already back then that we had discovered something really special. Thanks to the Neuron Foundation, we acquired a mobile LIDAR scanner, which allows us to measure the entire cave and the entire area of the lake. We will also cooperate with hydrologists who will measure the underwater portion of that lake using sonar.”

The latest technology was used by the Czech team; GeoSlam, a type of 3D scanning technology, has created accurate models of the cave. The process by which the cave containing the lake is made is also unusual. The lake’s mineral water is saturated with hydrogen sulfide, which, upon contact with air, oxidises and produces sulphuric acid that repeatedly turns the limestone rock into soft gypsum. The Czech team’s work in Albania will contribute to understanding this rare type of cave formation, and there is more work to be done there, as Richard Bouda explains:

“Thanks to the scientists we work with, we know that the surrounding springs are fed with water from the lake. We believe this discovery could also contribute to the protection of the whole area and to a better understanding of its hydrology, because to this day, nobody knows how exactly these underground waters are connected to the surface.”