Dominating the upper end of Yosemite Valley is a Half Dome, a rock formation that is both striking and unique. Its summit is 4,748 feet above the valley floor and 8,842 feet above sea level. Yosemite's Indians called it Tis-sa-ack, after the principal character in one of their legends. The last 200 years of the Half Dome hike are so steep that steel cable hand rails are provided for assistance. In Summer, about 600 people a day make the ascent.