There's a lake that's a giant sinkhole - Apparently.
Lake Vostok, located in Antarctica, is a massive subglacial lake that's approximately 250 miles long and 40 miles wide. It's a natural reservoir that's been sealed off for millions of years, with a crust of ice up to 13,000 feet thick. Scientists estimate that the lake holds around 15,000 cubic kilometers of water, roughly the same volume as Lake Baikal in Russia.