stylistic:tone
Topography

According to the United States Census Bureau, St. Louis has a total area of 66 square miles (170 km), of which 62 square miles (160 km) is land and 4.1 square miles (11 km) (6.2%) is water. The city is built on bluffs and terraces that rise 100–200 feet above the western banks of the Mississippi River, in the Midwestern United States just south of the Missouri -Mississippi confluence. Much of the area is a fertile and gently rolling prairie that features low hills and broad, shallow valleys. Both the Mississippi River and the Missouri River have cut large valleys with wide flood plains.

Limestone and dolomite of the Mississippian epoch underlie the area, and parts of the city are karst in nature. This is particularly true of the area south of downtown, which has numerous sinkholes and caves. Most of the caves in the city have been sealed, but many springs are visible along the riverfront. Coal, brick clay, and millerite ore were once mined in the city. The predominant surface rock, known as St. Louis limestone, is used as dimension stone and rubble for construction.

Near the southern boundary of the city of St. Louis (separating it from St. Louis County) is the River des Peres, practically the only river or stream within the city limits that is not entirely underground. Most of River des Peres was confined to a channel or put underground in the 1920s and early 1930s. The lower section of the river was the site of some of the worst flooding of the Great Flood of 1993.

The city's eastern boundary is the Mississippi River, which separates Missouri from Illinois. The Missouri River forms the northern line of St. Louis County, except for a few areas where the river has changed its course. The Meramec River forms most of its southern line.