Northern Indiana is a glaciated lake area, separated by the Wabash River from the central agricultural plain, which is rich with deep glacial drift. The southern portion of the state is a succession of bottomlands interspersed with knolls and ridges, gorges and valleys. Limestone caves, such as the big Wyandotte Cave, and mineral springs, as at French Lick and West Baden Springs, are found there. The unglaciated soil is shallow in S Indiana, and the cutting of timber has caused erosion, but there is still extensive farming.
The capital and largest city is Indianapolis, in the central part of the state. Indiana Dunes National Lakeshore, with a 3-mi (4.8-km) frontage on Lake Michigan, is noted for its beautiful shifting sand dunes. Formerly a state park, the area was made a National Lakeshore in 1966. Four years earlier, in 1962, the U.S. Congress authorized the establishment of the Lincoln Boyhood National Memorial in S Indiana. The Indianapolis Motor Speedway is the site of the famous 500-mi (800-km) auto race, held annually.