Fort Rock is a volcanic landmark called a tuff ring, located on an ice age lake bed in north Lake County, Oregon, United States.The ring is about 4,460 feet (1,360 m) in diameter and stands about 200 feet (60 m) high above the surrounding plain. Its name is derived from the tall, straight sides that resemble the palisades of a fort. The region of Fort Rock Basin contains about 40 such tuff rings and maars and is located in the Brothers Fault Zone of central Oregon's Great Basin.