Back in late spring of 2015, we took a trip out to Flagstaff seeking some cooler temperatures. One of the places we stopped at was the Lava River Cave.
Formed in the Pleistocene, roughly 675,000 years ago, this
Otherwise, it is your typical lava tube: dark and a bit chilly. (Occasionally, you can even find some ice in the entry.) To get in, you will have to climb over some rough boulders that have broken down from the ceiling, but once you are passed this difficult spot the floor flattens out and the walking becomes easy.