Photographs of Great Smoky Mountains National Park in the wee hours of the morning could entice even the most nature-hating urbanite to visit. Other stunning sights, like mountains misted by blue haze and more than a hundred leafy trails (it has the most trails of any national park), attract masses to the park. In fact, with more than 12 million visitors yearly, the popular destination is America's most visited national park. Visit in real life, and hordes of people, coupled with traffic jams, turn the outdoorsy haven into a headache. It's so bad that some visitors turn back and forget their trip altogether.