Castle Island Park & Fort Independence

South Boston lays claim to one of the city's most appealing shoreline parks: the 22-acre Castle Island. It's also among the oldest fortified military sites in North America, centerpieced by Fort Independence, a pentagonal granite structure that was finished in the 1850s. Prior to its construction, seven other forts had been built and destroyed in the area, occupied by American and British troops in turn. Today, the island's green space and open air make for a pleasant outing.