Mesa Verde National Park
Mesa Verde is the only National Park dedicated to preserving something built by humans; the rest focus on protecting the natural environment. This park is unique because the culture that inhabited this area did so for seven hundred years, from around 550 to the late 1270s. There are over 5,000 archaeological sites in its 80 square miles, 600 of which are cliff dwellings. What’s also noteworthy is that those cliff dwellings weren’t even built until the late 1190s. They were occupied for less than a hundred years before the people who built them headed south to what is now Arizona and New Mexico.
Why did they build their homes in caves on the side of a mountain? Why did they leave? No one knows.