Lava River Cave is a 1.2-kilometre lava tube in the Coconino National Forest, about 25 kilometres north of Flagstaff near Hart Prairie Road. It is one of the longest accessible lava tubes in the American Southwest, and unlike many tourist caves, it has no electricity or lighting — you bring your own and explore in genuine darkness.
The cave descends from the entrance into a wide tunnel that narrows in places and requires some ducking. At the far end, the tunnel becomes too low to continue. The round trip takes most people about an hour. Bring two light sources per person (the rule the National Forest Service recommends), warm layers, and shoes with grip. The cave floor is rough volcanic rock. In early spring, an ice plug sometimes blocks the entrance until late May.