"Diana's Punchbowl, also called the Devil's Cauldron, is a geothermal feature located on a small fault.  It is located in central-western Nevada, in the Monitor Valley, about 30 miles southeast of Austin, Nevada in Nye County."

See: http://en.wikipedia.org/wiki/Diana's_Punchbowl

Diana's Punchbowl was pretty impressive.  I parked the truck down below although as I was driving from the Monitor Valley road over to the punchbowl there was a 4wd truck up on top near the hole.  They were gone by the time I parked.  I have read elsewhere on the internet that the water temperature is around 180 degress F.  There was a sulfur smell in the air also at the punchbowl.