Almost all of Nevada belongs physiographically to the Great Basin, a plateau characterized by isolated mountain ranges separated by arid basins. These ranges generally trend north–south; most are short, up to 75 mi (121 km) long and 15 mi (24 km) wide, and rise to altitudes of 7,000–10,000 ft (2,100–3,000m). Chief among them are the Schell Creek, Ruby, Toiyabe, and Carson (within the Sierra Nevada). Nevada's highest point is Boundary Peak, 13,140 ft (4,007 m), in the southwest.
Nevada has a number of large lakes and several large saline marshes known as sinks. The largest lake is Pyramid, with an area of 188 sq mi (487 sq km), in the west. Nevada shares Lake Tahoe with California, and Lake Mead, created by Hoover Dam on the Colorado River, with Arizona. The streams of the Great Basin frequently disappear during dry spells; many of them flow into local lakes or sinks without reaching the sea. The state's longest river, the Humboldt, flows for 290 mi (467 km) through the northern half of the state into the Humboldt Sink. The Walker, Truckee, and Carson rivers drain the western part of Nevada. The canyon carved by the mighty Colorado, the river that forms the extreme southeastern boundary of the state, is the site of Nevada's lowest elevation, 479 ft (146 m).