The city has a total area of 319.03 square miles (826.28 km2), of which, 314.95 square miles (815.72 km2) is land and 4.08 square miles (10.57 km2) is water.[1] Bluffs overlook the rivers and river bottom areas. Kansas City proper is bowl-shaped and is surrounded to the north and south by glacier-carved limestone and bedrock cliffs. Kansas City is situated at the junction between the Dakota and Minnesota ice lobes during the maximum late Independence glaciation of the Pleistocene epoch. The Kansas and Missouri rivers cut wide valleys into the terrain when the glaciers melted and drained. A partially filled spillway valley crosses the central city. This valley is an eastward continuation of the Turkey Creek Valley. It is the closest major city to the geographic centre of the contiguous United States, or "Lower 48".