largest caldera (volcanic crater) in the Dyngjufjöll volcanic massif, in east-central Iceland. It lies 20 miles (32 km) north of Vatnajökull, the island's largest ice field. Its rugged peaks, up to 4,954 feet (1,510 m) above sea level, encircle a 4.25-square-mile (11-square-kilometre) lake that occupies the caldera. Askja (Icelandic: “Box”) is the highest peak in the Dyngjufjöll; surrounding it is the Ódádhahraun, an extensive lava field covering 1,422 square miles (3,681 square km). The volcano erupted in 1875 and again in 1961.