Czech researchers confirmed the existence of the world's largest underground thermal lake, named Lake Neuron, in southern Albania, first discovered in 2021. The recent expedition utilized measuring tools to determine the lake's dimensions and volume.
The team, funded by the Neuron Foundation, employed mobile LIDAR scanners to accurately map the subterranean lake, which is accessible only via a 100-meter-deep shaft. The lake measures 138.3 meters in length, 42 meters in width, and holds approximately 8,335 cubic meters (295,054 cubic feet) of hot, mineral-rich water—equivalent to around 3.5 Olympic-sized swimming pools.
"Thanks to more precise measuring tools, including a mobile LIDAR scanner supported by the Neuron Foundation, we were able to confirm the exceptional discovery of the world's largest underground thermal lake," said Marek Audy, the head of the recent expedition. "In order for Czech science to present this unprecedented discovery, it was necessary to conduct scientific research and precise measurements."
As reported by Focus Online, the lake was initially discovered during an exploration of the area around the city of Leskovik, where the team observed a large amount of steam emanating from a mountain range.
"Upon closer examination, we found that the steam was rising from an abyss," explained cave researcher and expedition member Richard Bouda. "During our initial exploration, we created a simple map of the place with our few tools and quickly realized that we had just discovered something extraordinary."
At the time of the initial discovery, the team lacked the proper instruments to measure the lake accurately. "Czech researchers first found this geothermal lake four years ago but did not have the necessary tools to measure it at that time." The recent expedition remedied this by using laser scanning technology, allowing the team to map the Atmos Cave leading down to Lake Neuron and three adjacent cave systems.
The region's complex geology played a crucial role in the formation of Lake Neuron. In karst regions like the Balkans, many caves exist because limestone has been hollowed out by carbonic acid rainwater over millions of years. The lake itself is saturated with hydrogen sulfide, which gives the water and steam a distinct smell of rotten eggs and is toxic.
The researchers hope that this discovery will enhance the understanding of underground ecosystems and geological processes. "We think this discovery will help protect the area and better understand the principle of water flows," said Bouda, according to GEO France. "Until now, no one has ever managed to explain precisely how underground waters are connected to the surface."
Despite challenges posed by the politically sensitive border area between Albania and Greece, which has been tense for over a century and sometimes makes research permits difficult to obtain, the team plans to continue their exploration.
"We want to look at other parts of the cave, learn more about the geology and biology of this area," Audy told National Geographic CZ.
Lake Neuron's discovery surpasses previous records held by similar geothermal lakes. The team had previously found a similar but smaller geothermal lake in Hungary, located beneath the Turkish baths in Budapest, which was considered the largest active thermal water cave until the discovery of Lake Neuron. "In 2008, we found a similar lake in Hungary, located beneath the Turkish baths, which until now was considered the world's largest active thermal water cave," said cave researcher Kalinovits Sándor.
This article was written in collaboration with generative AI company Alchemiq