PHOENIX -- The 'Bottomless Pit' in the Flagstaff area has been an attractive nuisance for more than a century. The name is somewhat misleading. It's called the bottomless pit but it's not.
"It's open fractures and cave features as far down as 2,000 feet below the surface," said Don Bills with the U.S. Geological Survey in Flagstaff.
During heavy rain and runoff, the Rio de Flag pools with water, filling up this deep hole, which lies on private property, before it eventually disappears into the ground.
"In 1988 there was actually a lake starting to develop there. People went out there, heard a roar and found nothing but a big hole in the ground," Bills said.
He is among the few allowed to see the pit.
"It's fenced off and the property owner realizes it can be a hazard and are sensitive to that."
In 1991 two boys climbed into the pit to explore and got stuck. They had to be rescued by fire crews.