Big Hole

Big Hole is a large maar (explosion crater) in the Fort Rock Basin of Lake County, central Oregon, northeast of Crater Lake, near Oregon Route 31. It is approximately 6000 ft (1820 m) across and 300 feet (91 m) deep. It is close to another smaller, but less-eroded maar crater, Hole-in-the-Ground.

http://en.wikipedia.org/wiki/Maar