Wisconsin can be divided into four main geographical regions, each covering roughly one-quarter of the state's land area. The most highly elevated of these is the Superior Upland, below Lake Superior and the border with Michigan. It has heavily forested rolling hills but no high mountains. Elevations range from about 700 ft (200 m) to slightly under 2,000 ft (600 m). A second upland region, called the Driftless Area, has a more rugged terrain, having been largely untouched by the glacial drifts that smoothed out topographical features in other parts of the state. Elevations here reach more than 1,200 ft (400 m). The third region is a large, crescent-shaped plain in central Wisconsin; its unglaciated portion is a sandstone plain, broken by rock formations that from a distance appear similar to the buttes and mesas of Colorado. Finally, in the east and southeast along Lake Michigan lies a large, glaciated lowland plain, fairly smooth in the Green Bay-Winnebago area but more irregular on the Door Peninsula and in the south.
Wisconsin's mean altitude is 1,050 ft (320 m), with elevations generally higher in the north. The Gogebic Range, extending westward from Michigan's Upper Peninsula into northern Wisconsin, was an important center of iron mining in the early days of statehood. Timms Hill, in north-central Wisconsin, is the state's highest point, at 1,952 ft (595 m). The lowest elevation is 579 ft (177 m), along the Lake Michigan shoreline.
There are well over 8,000 lakes in Wisconsin. Lakes Michigan and Superior form part of the northern and eastern borders; the Wisconsin mainland has at least 575 mi (925 km) of lakeshore and holds jurisdiction over 10,062 sq mi (26,061 sq km) of lake waters. By far, the largest inland lake is Lake Winnebago, in eastern Wisconsin, covering an area of 215 sq mi (557 sq km).
The Mississippi River, which forms part of the border with Minnesota and the entire border with Iowa, is the main navigable river. The major river flowing through the state is the Wisconsin, which follows a south-southwest course for 430 mi (692 km) before meeting the Mississippi at the Iowa border. Other tributaries of the Mississippi are the St. Croix River, also part of the Minnesota border, and the Chippewa and Black rivers. Located on the Black River are Big Manitou Falls, at 165 ft (50 m) the highest of the state's many waterfalls. Waters from the Fox River and its major tributary, the Wolf, flow into Green Bay and then into Lake Michigan, as does the Menominee, which is part of the Michigan state line.
Except in the Driftless Area, glaciation smoothed out many surface features, gouged out new ones, and left deposits of rock and soil creating distinctively shaped hills and ridges. Oval mounds, called drumlins, are still scattered over the southeast; and moraines, formed by deposits left at the edges of glaciers, are a prominent feature of eastern, central, and northwestern Wisconsin. In one section, called the Dells, the Wisconsin River has cut a gorge through 8 mi (13 km) of sandstone, creating caves and interesting rock formations.