Unseen mountains, valleys, lakes, and rivers lie under Antarctica’s mile-thick ice sheet. Changes to those hidden rivers could have dramatic global consequences.

Antarctica’s total ice volume is now estimated at 27.17 million cubic kilometers (6.52 million cubic miles). The ice sheet covers an area of 13.63 million square kilometers (5.26 million square miles), with an average thickness of 1,948 meters (6,391 feet).

The place thought to have had the thickest overlying ice was Astrolabe Basin, in Adélie Land, but a reinterpretation of data reveals it is in fact an unnamed canyon - at 76.052°S, 118.378°E in Wilkes Land, where the ice here is 4,757m thick, which is more than 15 times the height of the UK's tallest skyscraper, the Shard in London.