Hiking to Half Dome in Yosemite National Park is a serious undertaking, not suited to those who aren’t in good shape. The round-trip trek can reach 16 miles and last up to 12 hours, and the final 400 feet of ascent rely on two metal cables bolted into the rock. Despite the challenge, park records note that relatively few fatalities have occurred on the cables; nonetheless the route requires preparation, caution and respect for mountain conditions.