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To the north, the Harlem River divides 曼哈顿 Island from Bronx and the mainland United States. Several small islands are also part of the borough of 曼哈顿, including Randall’s Island, Wards Island, and Roosevelt Island in the East River, and Governors Island and Liberty Island to the south in New York Harbor. 曼哈顿 Island is 22.7 square miles (59 km2) in area, 13.4 miles (21.6 km) long and 2.3 miles (3.7 km) wide, at its widest (near 14th Street).
曼哈顿 is loosely divided into Downtown (Lower 曼哈顿), Midtown (Midtown 曼哈顿), and Uptown (Upper 曼哈顿), with Fifth Avenue dividing 曼哈顿’s east and west sides. 曼哈顿 Island is bounded by the Hudson River to the west and the East River to the east.
The bedrock underlying much of 曼哈顿 is a mica schist known as 曼哈顿 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 曼哈顿 Schist occur and Rat Rock is one rather large example.