The Great Sand Dunes Wilderness is the world's highest (and probably strangest) dune field. Rising over '700 feet above the valley floor, the age of this 50 square-mile pile of sand is still not precisely known. Official dating puts its age at less than 11,000 years, but it could be older. Some of the earliest traces of man in North America can be found within a few miles of this enigmatic wonder. Man may have visited here before the dunes were formed.