Travelling on the U1

It is the oldest underground line in Berlin. Nine kilometres, 13 stations. It was built at the end of the 19th century – largely as an overhead railway. Each station along the line is unique. Just like the passengers. There's a good reason why in "Linie 1", the most successful musical of all time in Berlin, they sang: "Take the underground / you won't need TV, TAZ or FAZ / trashy novels or ghost trains." So, all aboard please!

Warschauer Strasse. Terminus station. The doors open and suddenly the platform is full of people. Some want to get out, others want to get on. It's very crowded, as there's only one exit. A woman fights her way through the crowds with a pushchair. A couple walk by, arm in arm, leaning on each other – him with a plaster under his eye, her wearing sunglasses. The train is due to leave in six minutes.

13.47. "Train to Uhlandstrasse. All aboard please. Stand back from the doors." The doors close. Train number 715 starts rolling, jolting, jerking, hissing, squeaking. Then, after just a few seconds, it brakes, slowing to a walking pace as it crosses Oberbaumbrücke bridge, offering the most fantastic views you're ever likely to get from an underground train. To the right the TV tower, to the left the warehouse district. And below, the River Spree: the former border between east and west Berlin that separates the districts of Friedrichshain and Kreuzberg. This is followed by a long bend, and then the train is already pulling in at Schlesisches Tor in the heart of the trendy Kreuzberg district. Outside the chestnut trees are in bloom, the sun is reflecting off the windows of the old buildings, people are strolling along the streets and packing into the cafés. 13.49. "Stand back from the doors please."

A woman holding a cup of coffee has got on, another with a sheet of balsa half the size of a door. Both stay standing, there are no seats free. A man reads a newspaper, a girl listens to music, another is texting on her mobile and someone else is looking at pictures on his camera. Between them is a woman with her eyes closed. There's a constant murmuring in the background.

13:51. Görlitzer Bahnhof. Two musicians get on with an accordion and a trumpet. We all know what's coming: 30 seconds of music, then one of them goes around with a crumpled coffee cup. The passengers roll their eyes. A twenty-year-old in an RAF T-shirt and combat boots snaps: "anyone who gives them money is naive." Kottbusser Tor. The musicians get off and a ticket controller gets on. People roll their eyes again. Meanwhile, the landscape outside has changed considerably. Grey concrete buildings from the 1970s line the route, a satellite dish at every window. Walls splattered with paint bombs and graffiti, blinds drawn. This is the other side of Kreuzberg.

13.54. Prinzenstrasse. The underground passengers are at their most widely mixed here. Russian, Spanish, Turkish, Polish and English are to be heard, as well as German in a variety of dialects. A woman takes a pink mirror out of her handbag and puts on her lipstick.
13.56. Hallesches Tor. All of a sudden the train is half empty and the average age of the remaining passengers has doubled. The next stop is Möckernbrücke. A clear view of Potsdamer Platz, crossing over Landwehr Canal, looking over the rooftops of Berlin, the Gleisdreieck intersection. 14.00 exactly, the train sets off into the darkness. Everything goes black. Lamps flash by every second, and you can see a couple of pipes. It smells musty - a mix of oil, dirt and damp. Welcome to the underground, at Kurfürstenstrasse.

It is 14.02. Somewhere a small boy is counting to himself: "171, 172, 173..." The train stops at Nollendorfplatz and it's full again. A man in his mid-forties gets on, greets the passengers exuberantly and invites them to buy the homeless magazine "Motz". A woman grabs her purse. Wittenbergplatz. "195, 196, 197...", the boy gets out. "198, 199 – one thousand!" His mother interrupts him. "What comes after 100?" A brief silence. Eyes open wide. "200!", she explains. "Stand back from the doors please." The doors close, and the race is on. In the tunnel next door the U2 is heading for Ruhleben. First it overtakes us, then it hangs back. The U1 wins. Kurfürstendamm.

14.09. After a journey time of exactly 22 minutes, the train stops at Uhlandstrasse. "Terminus station. Train stops here." Everything here is clean, sterile and blue: the waiting shelters, the roof, the Ionic columns, the benches. Old photographs on the walls. The train sets off. Suddenly all is quiet. All you can hear is someone hurrying along in a pair of high heel shoes. And the sound of the ticket validation machine at the other end of the platform. Seconds later an empty train, number 714, arrives at the platform opposite. It is the U1 for Warschauer Strasse.