Montezuma Well National Monument
Montezuma Well, a detached unit of Montezuma Castle National Monument, is a natural limestone sinkhole near Rimrock, Arizona through which some 1,400,000 US gallons of water flow each day through two underground springs. It is located 11 miles (18 km) northeast of Montezuma Castle. The well measures in at 368 feet (112 m) across and 55 feet (17 m) deep. The water is highly carbonated and contains high levels of arsenic. At least five endemic species live (only) in the Well: a diatom, a springtail, a water scorpion, the amphipod, and the leech — the most endemic species in any spring in the Southwestern United States. It is also home to the Montezuma Well springsnail. Montezuma Well’s outflow has been used for irrigation since the 8th century. Part of a prehistoric canal is preserved at the picnic ground, and portions of the original Sinagua canal are still in use today.