The huge blocks of erosion-resistant granite left behind define Yosemite's landscape today. NASA Earth Observatory image by Robert Simmon, using Landsat 8 data from the US Geological Survey.

U.S. News Insider Tip: Traffic is hectic in and out of Yosemite Valley. The National Park Service advises travelers to arrive before 8 a.m. to avoid hourslong delays. – Catherine Parker Unless ...