Rapa Iti is the southernmost inhabited island in the Austral Islands group and the most isolated. It extends on the flanks of an ancient volcano, Mount Perau. The ocean has filled its crater after the collapse of one of its faces. Ahurei, the capital of the island, is located at the edge of the submerged crater, on both sides of the eponymous bay. The language of the island, the Reo Rapa, is different from other Southern languages.