Scientists have confirmed the world’s largest underground thermal lake inside a cave in southern Albania, following a recent expedition that mapped the site in detail. The lake, named Neuron, was first discovered four years ago by a team of Czech researchers. At the time, they lacked the necessary tools to measure its size. In 2024, with funding from the Neuron Foundation, the team returned with advanced 3D scanning technology, confirming it as the largest known underground hot water lake.
According to expedition leader Marek Audy, the lake spans 454 feet (138 meters) in length and 138 feet (42 meters) in width. It holds approximately 294,350 cubic feet (8,335 cubic meters) of water, the equivalent of 3.5 Olympic swimming pools.
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Discovery in a restricted region
The researchers first encountered the hidden lake while exploring a remote cave system along the Albania-Greece border. The region had been largely off-limits to scientific exploration due to long-standing political tensions.
While surveying the Leskovik area, the team spotted a large column of steam rising from a mountain range. Upon closer inspection, they traced it to a deep abyss more than 330 feet (100 meters) below the surface.
Descending into the pit, they uncovered an extensive network of caves, including some with thermal springs. One chamber housed the vast underground lake.
“During our initial exploration, we created a basic map using our equipment and immediately realized that we had discovered something extraordinary,” photographer and expedition member Richard Bouda said.
Mapping the hidden lake
In 2023, the team returned with a lidar scanner, a laser-based remote sensing device used for creating precise 3D models. The data confirmed the lake’s immense size and unique thermal properties.
Audy said the team aims to return for further studies. “It’s something that could have a huge impact on understanding underground ecosystems and geological processes,” he said. “We want to look at other parts of the cave, learn more about the geology and biology of this area.”
Comparison to previous discoveries
The discovery of Lake Neuron surpasses a similar find in Hungary, previously believed to be the world’s largest underground thermal lake. That site, located beneath historic Turkish baths in Budapest, was reported in 2008 as the biggest active water-filled thermal cave at the time.
Cave explorer Sandor Kalinovits, who helped discover the Hungarian lake, described it then as an unprecedented find. However, the recent expedition in Albania now places Lake Neuron as the largest known of its kind.
As research continues, scientists hope the site will provide further insights into the natural forces shaping the underground world.