Devil's Hole is a one of a kind geological feature. It is a geothermal pool that delves down through a series of caverns within the limestone bedrock. The hole is estimated to be 500 feet deep, but the bottom has never actually been found. The deep pond is home to the Devil's Hole Pupfish, so named because the entire species is only found in this body of water and are considered to be the world's rarest fish. The devil's Hole Overlook is an impressive fully enclosed bridge that takes visitors above the water.
If you go:
The road to Devil's Hole is unpaved but mostly in good shape. There is an 800 foot trail from the road to the overlook that is marked and not difficult. Due to the small size of the Devil's Hole Pupfish, you won't be able to see them from the overlook.
Links:

Devil's Hole Road
Pahrump, Nevada 89060 USA
desertcomplex@fws.gov
Mailing address:
610 East Springs Meadows Road
Amargosa Valley, Nevada 89020 USA
Phone Numbers:
Ash Meadows Visitors Center
+1 (775) 372-5435
+1 (775) 372-5435
Message from RoadTrip America