Montezuma Castle National Monument

The name is wrong on both counts. When European-Americans first observed the ruins in the 1860s, they named the site for the Aztec emperor Montezuma — a connection that never existed. The dwelling had been depopulated more than forty years before Montezuma was born. Built by the Southern Sinagua between 1125 and 1173 AD, the five-story, 20-room structure sits 90 feet up a sheer limestone cliff above Beaver Creek, its walls cut almost entirely from limestone found at the cliff's base. One of the best-preserved cliff dwellings in North America — and you can't go inside. Access has been closed since 1951.