A big wall is either a huge cliff or a long technical climbing route up that tall cliff. Examples of big walls are 3,000-foot-high El Capitan in Yosemite Valley and the 2,500-foot-high Painted Wall in Colorado. There is no exact definition of how tall a cliff has to be a big wall, but most are over 1,000 feet high. Climbing a big wall route usually takes several days of effort, although some spidermen climbers ascend them in a day. Find out more about speed climbing The Nose of El Capitan, a 3,000-foot big wall, at Speed Climbing on the Nose. Climbers sleep on big walls on a ledge or on a portaledge. Spending the night outside on a climb is called a bivouac.