Credit: Timothy Faust / Getty Images

Stretching over the western slopes of California's Sierra Nevada mountain chain, Yosemite is perhaps best known for its dramatic waterfalls – and its world-class climbing. El Capitan and Half Dome draw thousands of climbers each year to Yosemite Mountaineering School, which guide climbs throughout the park. 

Don't Miss: In 1919, metal cables were installed at the Half Dome to help visitors climb the last 400 feet to the summit without additional equipment. "Even though you put on gloves and walk along these cables with a bunch of other people, you do it after a long day of hiking and are completely jelly legged," said Jeffrey Olson, who works for the National Park Service. "You are wiped out when you get up there."