U字谷
Along the trail, the Merced River is a tumultuous mountain stream, lying in a U-shaped valley. Enormous boulders, some the size of a house, are dwarfed by the sheer faces of exfoliating granite, which rise 3000 feet (914 m) from the river. Through it all, the Merced River rushes down from its source in the High Sierra, and broadens on the floor of Yosemite Valley.