Aniakchak National Monument and Preserve features the Aniakchak Caldera, a crater nearly six miles in diameter and covering over ten square miles, which is the result of a series of eruptions. Surprise Lake, located within the caldera, is the source of the Aniakchak River, which flows down through a 1,500-foot gash in the caldera wall.
There are no trails in the monument - ash fields provide hiking/backpacking opportunities. Access to the park is by plane or float plane from King Salmon.
