Refugi 307 is four hundred metres of tunnel that a neighbourhood dug for itself. From 1937 the residents of Poble-sec cut into the soft rock at the foot of Montjuïc with hand tools, paying for the work out of their own pockets. The passage is a metre and a half wide and two metres high, cold, narrow and uneven underfoot. It was one of more than thirteen hundred shelters recorded across Barcelona, and the raids it was dug against came from airfields on Mallorca, nearly two hundred of them.
What makes this one worth going into is the fittings. It has a water fountain, a lavatory, an infirmary, a fireplace, and a room set aside for children. People expected to spend hours down here, repeatedly, so they built somewhere that could hold a family rather than a hole to run to. The walls are curved rather than square, because a rounded section spreads a shock wave instead of concentrating it. The visit goes at the pace of the group in front of you.