Rhode Island comprises two main regions. The New England Upland Region, which is rough and hilly and marked by forests and lakes, occupies the western two-thirds of the state, while the Seaboard Lowland, with its sandy beaches and salt marshes, occupies the eastern third. The highest point in the state is Jerimoth Hill, at 812 ft (248 m), in the northwest.
Rhode Island's principal river, the Blackstone, flows from Woonsocket past Pawtucket and thence into the Providence River, which, like the Sakonnet, is an estuary of Narragansett Bay; the Pawcatuck River flows into Block Island Sound. The state has 38 islands, the largest being Aquidneck (Rhode Island), with an area of about 45 sq mi (117 sq km).