More an apartment building than a castle, this cliff dwelling was built by members of the Sinagua tribe approximately seven centuries ago. Mistakenly associated with the Aztecs (thus the name), the complex is five stories high and features 20 rooms. Rising above creek flood plains, it could only be reached by ladder. Although visitors aren't permitted in the structure itself, they can view it from below and browse the visitors center. Eleven miles away is Montezuma's Well, a sinkhole that provided water for natives, along with an early irrigation network and other ruins.