Castle Island is a 22-acre urban park connected to the mainland by causeways. It is home to Fort Independence, a pentagon-shaped granite fort built between 1834 and 1851. The fort is actually the eighth one to be built here. The first fort on Castle Island was built in 1634.

The park is popular with families, who bring kids here to learn how to ride bikes, skateboard, roller-skate, climb on the play structures, splash in the water, and picnic. Since Castle Island is across the water from Logan International Airport, it’s a fantastic place to watch planes taking off and landing, and no matter what age your children are, they will be impressed by how close to the ground the planes seem to be.

The two paved walking paths—Pleasure Bay Loop, which is 1.84 miles long, and Castle Island Loop, which is less than 1 mile long and goes around the fort—offer views that can’t be beat.

Pleasure Bay, the M Street Beach, and Carson Beach, also part of the park system, stretch along 3 miles of parkland and beach on the South Boston shoreline of Dorchester Bay. From Carson Beach, a walkway leads from Castle Island to the Kennedy Library.

Remember: The Castle Island Association conducts guided tours of the fort from Memorial Day through Columbus Day; call ahead for hours, which vary. Keep your dog on a leash and clean up after it.

If you want to visit a real island (by boat), the nearby Boston Harbor Islands (Georges Island and Spectacle Island) make great day trips.

The popular snack bar serves hot dogs, chicken fingers, fries, ice cream, and other foods.