Craters of the Moon National Monument — Visitor Center and Lava Field Viewpoint

Craters of the Moon looks like the surface of another planet — and NASA actually sent Apollo astronauts here for geology training. The 7-mile paved loop road through the monument hits the main cinder cone cluster, spatter cones, and lava tube cave entrances. The visitor center has maps, flush toilets, drinking water, and rangers who actually know the geology. From the rim of the cinder cones you get a full panorama of the Snake River Plain volcanic corridor — the same landscape you’re driving across the whole western half of this trail system.

US-20/26/93 runs right along the monument boundary, making this an obvious stop when running the Hells Half Acre corridor. The monument is open year-round but the campground loop road and cave trails close in winter. Cell service is partial near the visitor center. No fuel on site — fill up in Arco (east) or Carey (west) before diverting in.

750 sq mi of black lava — Apollo training ground.