Shelter 307

When the Spanish Civil War brought aerial bombing to the city, the men of Poble Sec were already at the front. So it was the women, children and elderly who grabbed basic tools and started digging. What they built became Shelter 307, the 307th shelter registered with the city, which eventually had over 1,300 across Barcelona. Unlike most, this one goes horizontally into the mountain rather than straight down, and the tunnels zigzag deliberately so that a bomb blast at one end couldn't destroy the whole passage.

At its peak, 2,000 people sheltered here, on wooden benches, with roughly two hours of breathable air. There was a small infirmary, a children's play area, a kitchen and even a drinking fountain fed by groundwater from the mountain itself. Sleeping was forbidden, for practical reasons. But the house rules posted on the walls added two memorable lines: "Promoting pessimism is forbidden" and "Talking about politics is forbidden."

After the war, a glass factory was built on top, and the shelter was completely forgotten. For a while, poor migrant families from Granada actually lived in the tunnels, installing a chimney pipe that is still there today.