Part of the Museu d'Història de Barcelona (MUHBA), this is a shelter that dates back to the days of the Spanish Civil War. Barcelona was the city most heavily bombed from the air during the war and had more than 1300 air-raid shelters. Local citizens started digging this one under a fold of Montjuïc in March 1937.

Over the course of the next two years, the web of tunnels was slowly extended to 200m, with a theoretical capacity for 2000 people. People were not allowed to sleep overnight in the shelter – when raids were not being carried out work continued on its extension. Vaulted to displace the weight above the shelter to the clay brick walls (clay is porous, which allowed the bricks to absorb the shock waves of falling bombs without cracking), the tunnels were narrow and winding. Coated in lime to seal out humidity and whitewashed to relieve the sense of claustrophobia, they became a second home for many El Poble Sec folks.

When the civil war ended, Franco had some extensions made because he considered the option of entering WWII on Hitler’s side. When he decided not to join the war, this and other shelters were largely abandoned. In the tough years of famine and rationing during the 1940s and 1950s, families from Granada took up residence here rather than in the shacks springing up all over the area, as poor migrants arrived from southern Spain. Later on, an enterprising fellow grew mushrooms here for sale on the black market.

It's open only on Sundays by tour. Tours are conducted in English at 10.30am, Spanish at 11.30am and Catalan at 12.30pm. With limited spots, tours book up, so it's wise to reserve ahead.