The little country of Albania was recently discovered to be harboring a giant secret: the largest geothermally-heated underground lake in the world.

Discovered in 2021 by Czech scientists, geopolitical troubles on the border region with Greece saw them depart before a proper investigation of the cave could be made.

What they did find though was a massive column of steam rising out of the hills in an area around the town of Leskovik. Approaching it, they encountered a massive abyss descending 330 feet (100 meters) under the Earth. Exploring down, they found this massive lake of turquoise water that was geothermally heated.

Funded by a research grant from the Neuron Foundation, which supports pioneering scientists in Czechia, the team was able to return in 2024 for a proper study.

The scientists used state-of-the-art technologies during the expedition, including a mobile LiDAR scanner, which allowed for detailed mapping of the underground spaces. Precise geodetic measurements created a comprehensive map of the Atmos Cave and other nearby caves, such as Sulfur, Breška, and Kobyla, which were already discovered in 2021.

“It’s something that could have a huge impact on understanding underground ecosystems and geological processes,” Marek Audy, a caver and scientist in the research team, told Nat Geo CZ. “We want to look at other parts of the cave, learn more about the geology and biology of this area.”

The LiDAR survey produced a total size of 454 feet (138 meters) of length and 138 feet (45 m) of depth. With over 8,000 cubic meters of water, it contains more 3.5 Olympic swimming pools of water volume, making it larger than the previously-recognized subterranean heated lake in the world in Hungary.

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They named it Lake Neuron after the foundation that funded them.

“I am incredibly proud that we could support Czech scientists in such a groundbreaking project,” Monika Řasa Vondráková, director and co-founder of the Neuron Foundation, said in a statement.

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“This achievement underscores the importance of supporting scientists directly in the field, where their expertise and dedication lead to new discoveries. Expeditions like these are vital for advancing science and expanding our understanding of the world around us.”