Montezuma Well a detached unit of Montezuma Castle National Monument

Montezuma Castle National Monument

Montezuma Castle National Monument, located near Camp Verde, Arizona, in the Southwestern United States, features well-preserved cliff-dwellings. They were built and used by the Pre-Columbian Sinagua people, northern cousins of the Hohokam, around 700 AD. Several Hopi clans trace their roots to...

, is a natural limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

 sinkhole

Sinkhole

A sinkhole, also known as a sink, shake hole, swallow hole, swallet, doline or cenote, is a natural depression or hole in the Earth's surface caused by karst processes — the chemical dissolution of carbonate rocks or suffosion processes for example in sandstone...

 near Rimrock, Arizona through which some 1400000 gallons (5,299,576.8 l) of water flow each day through two underground springs. It is located 11 miles (17.7 km) northeast of Montezuma Castle. The well measures in at 368 feet (112.2 m) across and 55 feet (16.8 m) deep. The water is highly carbonated and contains high levels of arsenic

Arsenic

Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...

. At least five endemic species live (only) in the Well: the diatom

Diatom

Diatoms are a major group of algae, and are one of the most common types of phytoplankton. Most diatoms are unicellular, although they can exist as colonies in the shape of filaments or ribbons , fans , zigzags , or stellate colonies . Diatoms are producers within the food chain...

, the springtail

Springtail

Springtails form the largest of the three lineages of modern hexapods that are no longer considered insects...

, the water scorpion, the amphipod (Hyalella montezuma

Hyalella montezuma

Hyalella montezuma is a pelagic amphipod. It lives in Montezuma Well, an oasis in central Arizona. It is the only food of the endemic leech Motobdella montezuma....

), and the leech

Leech

Leeches are segmented worms that belong to the phylum Annelida and comprise the subclass Hirudinea. Like other oligochaetes such as earthworms, leeches share a clitellum and are hermaphrodites. Nevertheless, they differ from other oligochaetes in significant ways...

 (Erpodbella montezuma

Motobdella montezuma

Motobdella montezuma is a species of leech which is only found in Montezuma Well, central Arizona, United States. It is a nocturnal pelagic predator that feeds almost exclusively on the endemic amphipod Hyalella montezuma, which it detects using passive sonar and swallows whole.-Description:Adults...

) -- the most endemic species in any spring in the Southwestern United States. It is also home to the Montezuma Well springsnail

Montezuma well springsnail

The Montezuma Well springsnail, scientific name Pyrgulopsis montezumensis, is a species of very small freshwater snail that has an operculum, an aquatic gastropod mollusk in the family Hydrobiidae....

.

Montezuma Well's outflow has been used for irrigation

Irrigation

Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...

 since the 8th century. Part of a prehistoric canal is preserved at the picnic ground, and portions of the original Sinagua

Sinagua

The Sinagua were a pre-Columbian cultural group occupying an area in central Arizona between the Little Colorado River and the Salt River including the Verde Valley and significant portions of the Mogollon Rim country between approximately 500 AD and 1425 AD.Early Sinagua sites consist of pit houses...

 canal are still in use today.

The existence of the well was almost unknown to Anglo Americans before the publishing of Handbook to America by Richard J. Hinton in 1878. In 1968, Montezuma Well was the subject of the first ever underwater archaeological survey to take place in a National Park, led by archaeologist George R Fischer.

The Yavapai people

Yavapai people

Yavapai are an indigenous people in Arizona. Historically, the Yavapai were divided into four geographical bands that considered themselves separate peoples: the Tolkapaya, or Western Yavapai, the Yavapé, or Northwestern Yavapai, the Kwevkapaya, or Southeastern Yavapai, and Wipukpa, or Northeastern...

 believe they emerged into this world through the well, and as such, it is a very sacred place to them.

In recent years Illinois Pondweed (Potamogeton illinoensis) has invaded the well. Weekly maintenance is required to keep water from the well flowing.