The Great Sand Dunes can be found in Colorado, USA. They are located in the San Luis Valley and are notable for being the tallest sand dunes in North America, rising over 750 feet. The area was designated as a National Park and Preserve, preserving the unique ecosystem and providing recreational opportunities. Visitors can enjoy activities like sandboarding and hiking among the dunes, with stunning backdrops of the Rocky Mountains. This unique geographic feature is a result of ancient lake beds and wind patterns.