Dragon's Breath Cave, Namibia - The largest non-subglacial underground lake, discovered in 1986, named for the humid air that escapes from its entrance.
Clearwater Cave System, Malaysia - Part of the Mulu Caves in Sarawak, it houses one of the world's largest underground river systems.
Melissani Cave, Greece - Known for its stunning blue water, this cave was once worshipped as a place of the nymphs.
Devil's Hole, USA - An aquifer-fed cave pool in Nevada, home to the endangered Devil's Hole pupfish.
The Lost Sea, USA - Located in Tennessee, it is America's largest underground lake, featuring a boat tour for visitors.
St. Leonard's Cavern, Switzerland - Europe's largest underground lake, known for its crystal-clear water and boat tours.
Llangorse Lake, Wales - The largest natural lake in Wales, featuring prehistoric remains and an underwater viewing area.
Lake Vostok, Antarctica - A subglacial lake buried under 2.5 miles of ice, one of the largest and deepest lakes on Earth.
Reed Flute Cave, China - An iconic tourist attraction in Guilin, featuring an underground lake surrounded by stunning limestone formations.