The Bunkers del Carmel (officially Turó de la Rovira) are former Spanish Civil War anti-aircraft battery positions on a hilltop offering arguably the best panoramic views in Barcelona — and they're completely free. From 262 meters above sea level, you get a 360-degree vista encompassing the Sagrada Família, Torre Glòries, the Mediterranean coastline, Montjuïc, and the Collserola mountains. Originally built in 1938 to defend the city against aerial bombardment, the bunkers fell into disrepair before being rediscovered by locals as a sunset spot. Now a recognized heritage site, it remains far less crowded than Park Güell while offering superior views.