Significance
“Structures from the Stone Age can provide unique insights into Late Glacial and Mesolithic cultures around the Baltic Sea. Such structures, however, usually did not survive within the densely populated Central European subcontinent. Here, we explore a Stone Age megastructure, that has preserved under water in the Western Baltic Sea. It was likely constructed by hunter–gatherer groups more than 10000 y ago and ultimately drowned during the Littorina transgression at 8500 y B.P. Since then, it remained hidden at the seafloor, leading to a pristine preservation that will inspire research on the lifestyle and territorial development in the larger area.”