Manhattan is loosely divided into Downtown (Lower Manhattan), Midtown (Midtown Manhattan), and Uptown (Upper Manhattan), with Fifth Avenue dividing Manhattan’s east and west sides. Manhattan Island is bounded by the Hudson River to the west and the East River to the east.
The bedrock underlying much of Manhattan is a mica schist known as Manhattan Schist. It is a strong, competent metamorphic rock created when Pangaea formed. It is well suited for the foundations of tall buildings and the two large concentrations of skyscrapers on the island occur in locations where the formation is close to the surface. In Central Park, outcrops of Manhattan Schist occur and Rat Rock is one rather large example.