Castle Island sits at the tip of South Boston’s peninsula, a 22-acre state park where Boston Harbor history and waterfront recreation meet. Despite its name, it hasn’t been a true island since 1928, when a causeway permanently connected it to the mainland — but the sense of being surrounded by water remains, with sweeping views of Boston Harbor, the harbor islands, and planes descending into nearby Logan Airport.

The park’s centerpiece is Fort Independence, a striking granite fortress that has stood guard over the harbor since the colonial era. Free ranger-led tours run during summer months, revealing the fort’s role in every American conflict from the Revolution through World War II. Edgar Allan Poe was stationed here as a young soldier, and local legend claims the fort inspired his story “The Cask of Amontillado.”

The 1.5-mile paved loop trail circling the point is one of Boston’s most beloved walks — flat, stroller-friendly, and lined with benches facing the harbor. Fishing off the seawall draws regulars year-round, and the adjacent Pleasure Bay offers a calm, sheltered beach for swimming in summer. Sullivan’s, the iconic seasonal snack stand, has been serving hot dogs and lobster rolls to Castle Island visitors since 1951.

No camping is available on-site. The park is open year-round, but late May through October is prime season when fort tours run and Sullivan’s is open. Even in winter, the harborside walk draws locals chasing cold, clear views across the water.

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