What's enormous, volcanic and boasts the most must-see glaciers in the Lower 48? Washington state's 14,400-foot Mount Rainier, visible on a clear day from sea-level downtown Seattle. Rainier has 25 named glaciers and a number of contiguous-U.S. claims to fame: Emmons Glacier, with the largest surface area; Nisqually Glacier, with the fastest movement (about 2 feet per day); and 700-foot-thick Carbon Glacier, which flows all the way down to 3,500 feet elevation to meet you. Most of Rainier's glaciers are pulling back, which means that in the future, you'll have to climb higher to get up close to the big ice.