Easter Island was formed by three extinct volcanoes, each located at one corner of the triangle.  The Rano Kau volcano erupted around 2.5 million years ago, forming the southwestern part of the island. On the rim you will find Orongo Village, while the airport is located at the volcano’s base, between its slopes and the village of Hanga Roa.  Rano Kau is a shield volcano, with gentle slopes and a wide caldera approximately 1.6 km across.  Inside the crater is a large freshwater lake, sheltered from the strong winds and home to a number of plants found nowhere else on the island.  When the Rapa Nui civilization was flourishing, Rano Kau’s rich volcanic slopes provided important agricultural land, and the crater lake provided one of the few sources of fresh water available on the island.