Montjuïc Castle

• Old coastal cannons line the seaward ramparts, the kind kids can stand beside and sight along the barrel
• 360-degree terrace wraps the top with views over the port, the sea, and the city rooftops
• Free for under 16s, and free for all on Sundays after 3pm and the first Sunday of each month

An 18th-century military fortress on the 173-meter Montjuïc hill, built in a star shape with angled bastions, a dry moat crossed by a stone bridge, and a watchtower. Kids can walk the ramparts, peer through gun embrasures at the rusted coastal cannons, and cross the drawbridge into the parade ground. The wraparound terrace gives a 360-degree view over the harbor, the sea, and the rooftops below.