Montjuic Castle (Barcelona)

Montjuïc Castle is a historic, 17th-century military fortress perched 173 meters above the port in Barcelona. The very first fortress was thrown up in record time - just 30 days in 1640 during the Reapers' Revolt. Ironically, although built to protect Barcelona, the castle's cannons were turned on the city itself multiple times, most notably when Spanish forces bombarded it in 1842 to crush local uprisings.