Situated just west of Amboy along the National Trails Highway (Route 66), Amboy Crater is an impressive 250 feet high and 1500 feet in diameter. Equally impressive is its distinctive, symmetrical volcanic shape and it is this that earned its designation as a National Natural Landmark. The crater sits within 24 square miles of lava flow and can be visited from a day use site offering panic tables, restrooms and interpretive information.
If you go:
There's a 3-mile round trip trail that takes you around the rim (hiking this trail is not advised in the summer months). For a less challenging hike, there's a wheelchair accessible ramp trail leading to a shaded viewing platform no more than 100 yards from the car park.
Links:

National Trails Highway
Amboy, California 92304 USA
Mailing address:
BLM, Needles Field Office
1303 South U.S. Hwy 95
Needles, CA 92363 USA
Phone Numbers:
Bureau of Land Management
+1 (760) 326-7000
+1 (760) 326-7000