According to Native American legend, one of Yosemite Valley's early inhabitants went down from the mountains to Mono Lake, where he wed a Paiute named Tesaiyac. The journey back to the valley was difficult, and by the time they reached what was to become Mirror Lake, Tesaiyac had decided that she wanted to go back down to live with her people at Mono Lake. However, her husband refused to live on such barren, arid land with no oak trees from which to get acorns.
With a heart full of despair, Tesaiyac began to run toward Mono Lake, and her husband followed her. When the powerful spirits heard quarreling in Yosemite, they became angry and turned the two into stone: he became North Dome and she became Half Dome. The tears she cried made marks as they ran down her face, thus forming Mirror Lake.
Though its origins are mythical, there's no doubt that Half Dome is Yosemite's most distinctive natural monument. It is 87 million years old and has a 93% vertical grade - the sheerest cliff in North America. Climbers come from around the world to grapple with its legendary north face, but good hikers can reach its summit via a 17-mile round-trip trail from Yosemite Valley. The trail gains 4900ft in elevation and has cable handrails for the last 200yd. The hike can be done in one day, but is more enjoyable if you break it up by camping along the way (Little Yosemite Valley is the most popular spot).