There's a lake that's a giant sinkhole - Apparently.
Lake Vostok, located in Antarctica, is the largest subglacial lake on Earth, covering an area of approximately 14,000 square kilometers. It's estimated to be about 800 meters deep and contains 15,000 cubic kilometers of freshwater. The lake is separated from the surrounding ice by a 4-5 kilometer thick ice wall, which prevents it from draining. Scientists believe that Lake Vostok may hold unique ecosystems and could provide valuable insights into the Earth's geological history.