In Turkmenistan, a sun-scorched Central Asian country where over 80 percent of the land is covered in desert, finding a place to swim can often be a challenge.

The landlocked nation has access to the Caspian Sea, the world’s largest lake, but it’s a long way from the capital city of Ashgabat. Most people from the capital region prefer the country’s next best swimming spot—which is located more than 200 feet underground.

A long metal staircase leads down into the Bakharden Cave, where the 235-foot-long lake is located. The warm waters contain a high amount of different salts and minerals, most notably sulfur, which is responsible for the distinct smell within the cave. Thus, Köw Ata Underground Lake is also the closest thing Turkmenistan has to a thermal spa.

Aside from being a swimming spot and a thermal spa, the cave is also a natural monument, established to protect the largest known colony of bats in the whole of Central Asia. It is a question of personal taste, whether this fact adds to a pleasurable swim or not.