East Crater Ring

Crater Rings are adjacent, symmetrical volcanic pit craters in the Western Snake River Plain about 8 miles northwest of Mountain Home. They are one of few examples of volcanic craters in the continental United States. The craters are at the summit of a broad shield volcano. The eastern crater is about 3000 ft across and 350 ft deep. The western is 2500 ft across and 300 ft deep.
-from Wikipedia