Manhattan

Manhattan is an island 21.6 kilometers long and 3.7 kilometers wide (at its widest point).

An excerpt from the article 18 facts about Manhattan

Its area is 58.8 square kilometers. Manhattan Island is bounded by the Hudson River on the west and the East River on the east. To the north, the Harlem River separates the island from the Bronx and the continental United States. New York Bay is located south of Manhattan.