Castle Clinton National Monument

Castle Clinton National Monument is a historic circular fort located on the southern tip of Manhattan. Built between 1808 and 1811, this fascinating monument originally served as a coastal defense against British invasion.

Over the years, it has served a variety of functions - from an entertainment venue, to America's first immigration center (before Ellis Island), to an aquarium. Today, it's a popular tourist attraction where you can learn about New York's rich history and admire the early 19th century architecture.