Situated a half-mile south of Manhattan, the 172-acre Governors Island, was, for many years, a Coast Guard installation. Before that, it was an army post for nearly 200 years and played a part in the Revolutionary War. In April 2010, New York City took over. Because it was a military base for so long, few New Yorkers, much less tourists, had visited Governors Island. But that has changed. Much of Governors Island is now a public park and 22 acres on the island are already a national monument, centered around two 1812-era fortresses. The island is open to visitors from the end of May to October. During that time, you can take a free ferry from the Battery Maritime Building adjacent to the Staten Island Ferry in lower Manhattan. (There is also a ferry from Pier 6 in Brooklyn Bridge Park.) On the island, you can walk or bicycle in a car-free environment and attend any number of activities from jazz concerts to table tennis demonstrations.