Water divides several parts of the city. The Hudson River flows through the Hudson Valley into New York Bay. Between New York City and Troy, New York, the river is an estuary. The Hudson River separates the city from the U.S. state of New Jersey. Part of the Hudson River forms the border between Manhattan and the Bronx on one side, and the State of New Jersey on the other side. The East River forms the border between Manhattan on one side, and Brooklyn and Queens on the other side. The Harlem River forms the border between Manhattan and the Bronx (except for a small part of Manhattan that is on the mainland). Part of Long Island Sound separates the Bronx and Queens. Newtown Creek is part of the border between Brooklyn and Queens. Some parts of the city are very separate from the others because of water, such as Rockaway in Queens and City Island in the Bronx. A small piece of land in Manhattan is international territory and belongs to the United Nations Headquarters. The country of Somalia is the only country whose national flag copied the colors of the UN. The Bronx River, which flows through the Bronx and Westchester County, is the only entirely fresh water river in the city.