 Montezuma Well is geologically very similar to the sinkholes and cenotes found in Florida and the Yucatán peninsula of Mexico - that is, a limestone cave that has collapsed to expose its subterranean water source.The Well sits at the northern end of what is called the Verde Limestone formation, a distinct layer of travertine limestone - more than thick in some places - deposited beneath a series of shallow lakes that covered Arizona's central Verde Valley region between eight and two million years ago.Archaeological evidence suggests that humans have lived in the Verde Valley for at least 10,000 years.