Manhattan is the most densely populated of the five boroughs of New York City. The borough is coterminous with New York County, an original county of the U.S. state of New York. The borough mostly consists of Manhattan Island, bounded by the East, Hudson and Harlem Rivers, but also includes several small adjacent islands and a small area on the mainland. Manhattan has been described as the economic and cultural center of the United States, and is home to the United Nations Headquarters. Wall Street in Lower Manhattan has been called the financial capital of the world, has an estimated GDP of over $1.2 trillion, and is home of both the New York Stock Exchange and NASDAQ.