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.