15. Exploring Mesa Verde National Park

Mesa Verde National Park in Colorado is home to the largest archeological preserve in America. You can find the remains of a lost civilization hidden in the walls of park's canyons. These mysterious dwellings still hold many secrets and the thrill of discovery for those ready for a unique adventure. Greg set out to explore the park with Britt and Mike -- an active couple from Chicago who love the outdoors. They are both avid cyclist.