Mount Aniakchak is a 3,700-year-old volcanic caldera (about 10 kilometers (6 mi) in diameter) located in the Aleutian Range of Alaska, United States. The area around the volcano is the Aniakchak National Monument and Preserve, maintained by the National Park Service. In November 1967, Aniakchak Caldera was designated as a National Natural Landmark by the National Park Service.