Makronisos, or Makronisi, is an island in the Aegean Sea, in Greece, notorious as the site of a political prison from the 1920s to the 1970s. It is located close to the coast of Attica, facing the port of Lavrio. The island has an elongated shape, 13 km (8 mi) north to south and 2.5 km (1.6 mi) east to west at its widest point, and its terrain is arid and rocky. It is the largest uninhabited Greek island.