MNN Galleries

13 amazing sinkholes

By: Laura Moss on Oct. 6, 2010, 11:22 a.m.
Montezuma Well

Photo: Alexey Stiop/Shutterstock

11 of 15

Montezuma Well

Montezuma Well is located in Arizona’s Montezuma National Monument Park. The sinkhole was formed during prehistoric times when a limestone cavern collapsed, and today it’s 365 feet wide and 55 feet deep.

Some 1.4 million gallons of water flow through the sinkhole each day from underground springs. The water of Montezuma Well is highly carbonated due to high levels of carbon dioxide, and the water contains very little oxygen and high levels of arsenic so it can’t support fish.