Mesa Verde National Park in Colorado is both a National Park and a World Heritage Site. It was the first National Park we visited that was focused specifically around a peoples impact on the land. It is the site of a great Ancestral Puebloan city and the largest archaeological preserve in the US.
Above is a photo of the inside of the Sun Temple. Jim and I were alarmed when we visited this site because it has absolutely no doors. The Sun Temple is thought to have been an astronomical observatory. Its architecture is aligned to the lunar standstill (only occuring every 18.6 years) and the sunset during the winter solstice.
Square Tower
Although this photo of square tower was taken from above, it sits on top of a much larger canyon. So the Ancestral Puebloans had do be some crazy rock climbers to either climb up or down to this settlement after farming or hunting for the day.
Cliff palace
Nearby Mesa Verde is the Great Sand Dunes national park. These sand dunes in southern Colorado are the tallest sand dunes in North America. They were formed when large lakes in this area receded and the sand leftover in the lake beds was then blown towards the Sangre de Cristo Mountains.
You can rent sandboards and sleds just outside of the park. It is exhausting climbing up those dunes, but well worth the fast rides down the dunes (although we sure did get sand everywhere!)
The dunes lay inbetween the grasslands and the Sangre de Cristo mountains.