There's a lake that's a giant sinkhole - Apparently.
Lake Vostok, located in Antarctica, is a massive subglacial lake that's approximately 240 kilometers long and 50 kilometers wide. It's estimated to be around 20 million years old and has remained isolated from the surface for most of that time. The lake is surrounded by a thick layer of ice, and its surface is 400 meters below the surface of the surrounding ice sheet. Scientists have only recently begun to explore the lake through boreholes, revealing a unique ecosystem that's unlike anything found elsewhere on Earth.