In February 2025, it was reported that a team of Czech scientists discovered what is now considered the world's largest underground thermal lake.

Initially visiting as a kayaker, he noticed features in the landscape resembling areas with thermal caves, which inspired further exploration and ultimately led to the discovery.

[2][3] Czech researchers had been exploring underground formations in mountain valleys along the Albania-Greece border for several years.

In 2021, during an expedition in the Vromoneri Valley near Leskovik, Albania, they identified a large cave system with multiple thermal springs.

[4][5][3] The cave’s formation is unusual, as the lake’s mineral-rich water contains hydrogen sulfide, which oxidizes upon contact with air, producing sulfuric acid that continuously transforms limestone into soft gypsum.