These are America's most important National Monuments

Montezuma Castle has been a National Monument since 1906, though its history stretches back much, much further. This site preserves an impressive ancient cliff dwelling built by the indigenous Sinagua people almost 1,000 years ago – a 20-room, multi-story “castle” carved into a limestone cliff face. It’s often compared to a modern apartment block and it stands in central Arizona, surrounded by sycamores, whose wood was used to build support beams for the structure.