Desperate to escape the heat but still antsy to get outside in Arizona? Arizona's longest lava tube is worth exploring. The Lava River Cave was formed roughly 700,000 years ago, when the top and sides of a stream of molten lava cooled while the interior continued to flow, hollowing out the smooth-walled, arched tunnel that still exists today.

Entrance

While we considered this a very easy cave, the entrance is rocky and does require slow maneuvering.

The cave definitely gets a fair amount of visitors --all probably trying to escape the heat. I'd recommend starting early if visiting on a weekend and don't forget to bring plenty of lights. Maybe it was just a coincidence, but the day we went there seemed to be a few field trips going on there. It was the easiest non-paved cave we've explored but it was still fun.