About 100 kilometres east of Kingman on Historic Route 66, this dry limestone cave system descends 65 metres underground via lift. Discovered in 1927 by a woodcutter who fell into a sinkhole, the caverns are notable for their bone-dry air — there are no stalactites, no dripping water, and no living organisms, which preserves everything that gets left inside indefinitely. A 1920s-era pack rat skeleton is on display as evidence.
A single hotel room sits at the bottom of the cave — billed as the world's deepest, darkest, oldest, and quietest hotel room — and can be rented for the night if you like the idea of sleeping 65 metres underground. The above-ground complex includes a diner, motel, and gift shop along the longest unbroken stretch of original Route 66 anywhere.