Archaeologists have identified what may be Europe’s oldest human-made megastructure, submerged 21 meters below the Baltic Sea in the Bay of Mecklenburg, Germany. The evidence suggests it was constructed by Palaeolithic people between 11,700 and 9,900 years ago, probably as an aid for hunting reindeer. This revealed that the Blinkerwall stands on a ridge running east to west, with a 5km-wide lake basin a few meters above the ridge to the south.