Castle Island
Although it once was, Castle Island is no longer, well, an island. Capping the South Boston neighborhood, Castle Island is accessible by car and by foot from Day Boulevard. Its centerpiece is Fort Independence, built in 1801 (although there have been battlements on-site since 1644), open for free tours on summer weekend afternoons. Castle Island is a popular spot to walk dogs, jog, or cycle, whether just around the island itself or along the water-set Pleasure Bay Loop. There's also a nice playground for kids. Stop by Castle Island institution Sullivan's for a hot dog, fried seafood dinner, or ice cream. Views of the harbor and its outlying islands are expansive.