On our way to Arizona, we stopped at several places in Colorado. One of the most impressive man made wonders I have ever seen are the Mesa Verde Ruins in Mesa Verde National Park.
Carved and built into the side of a mountain by native peoples, it is almost an unbelieveable site! My brother and I were discussing how small the doorways were, when a ranger overheard us and explained that the average woman was 5'0" and the average man was 5'4"!
You can find alot of information at their website at:
*There is alot of uphill walking on narrow pathways. If you have heart trouble or other health issues, you may want to consider this...