The U-Bahn rumbles down the tracks to Nauener Platz station like a tame adult rollercoaster. Maybe it’s the perpetual luminosity in the Berlin underground that makes it so interesting to me. Outside it might be the loveliest late summer morning or the worst November evening, but once I move underground it is the same neon-lit brightness as at three in the morning on a Saturday, the same screaming beer-drunk punks, the same grey mice scurrying around between the smashed green Lech bottles on the tracks. The short ride down to Berliner Strasse feels like travelling in limbo.