Amboy Crater
A near-perfect black volcanic cinder cone rising from a 70-square-mile lava field, designated a National Natural Landmark beside old Route 66. A roughly 3-to-4-mile round-trip trail crosses the lava to climb into and around the crater rim — flat but fully exposed, so avoid the summer heat and carry plenty of water.
34°33'27.4"N 115°46'36.7"W (CA, San Bernardino County)

