Lake Pavin was formed in the crater of an ancient volcano carved out on the northern flank of Puy de Montchal at an altitude of 3,927 ft (1,197 m). Its surface area of 108,7 acres (44 ha) and its diameter of 2,460 feet (750 meters) occupy an almost perfectly circular depression cut out of pre-existing flows and pyroclastics. Its bottom, about 984 ft (300 m) in diameter at 305 ft (93 m) deep, is flat. It extends a little over 984 feet (300 meters) from the outlet to the north, while, on the cliffside to the south, the submerged slope is steeper and the bottom extends 492 feet (150 meters) from the edge.