Castle Clinton National Monument
Annual visitors: 4.6 million
Location: New York City
Size: 44,000 square feet
Founded: 1808
Highlights: Located on the Southern tip of Manhattan in Battery Park, Castle Clinton (originally known as Southwest Battery) was built to prevent a British invasion during the War of 1812. After the war, the building served as an immigration depot and then as home of the New York City Aquarium before being restored and re-opened in 1975.
