The Great Smoky Mountains, part of the Appalachian Mountains, have a wide range of elevations, making them home to over 400 vertebrate species, 100 tree species, and 5000 plant species. Hiking is the park's main attraction, with over 800 miles (1,300�km) of trails, including 70 miles (110�km) of the Appalachian Trail. Other activities are fishing, horseback riding, and visiting some of nearly 80 historic structures.