From the World Heritage inscription for Great Smoky Mountains National Park:
The Great Smoky Mountains National Park is a major North American refuge of temperate zone flora and fauna that survived the Pleistocene glaciations. The park includes the largest remnant of the diverse Arcto-Tertiary geoflora era left in the world and provides an indication of the appearance of late Pleistocene flora. It is large enough to allow the continuing biological evolution of this natural system, and its biological diversity exceeds that of other temperate-zone protected areas of comparable size. The park is of exceptional natural beauty with undisturbed, virgin forest including the largest block of virgin red spruce remaining on earth.
The Great Smoky Mountains National Park is the most visited national park in the United States, primarily due to its location near major population centers in Tennessee and North Carolina. In addition to its natural treasures, it also has historical significance. Churches and homes of many of the mountain people who lived in the area still stand today.
View the complete list of UNESCO World Heritage Sites in the United States.
View the list of all of the UNESCO World Heritage sites I have visited on my travels.