Oberbaum Bridge

Stand still for a moment and feel the bridge under your feet. Every few minutes, a low rumble rolls through the brick. A yellow train passes on the deck above you, and the whole structure carries a soft vibration. Below, the river Spree moves slowly, grey-green and wide. The air smells of water, diesel from passing boats, and on warm days, coffee from the cafes along the banks. This is the Oberbaum Bridge, and it has been joining two halves of Berlin for well over a century.

Look at its shape first. This is not a simple road bridge. It has two levels. The lower level carries cars, bicycles and people on foot. The upper level carries the underground railway, which here runs in the open air on a long arcade of brick arches. Two tall towers rise from the middle, with pointed roofs and narrow windows. From a distance, the bridge looks less like a piece of transport and more like a gate to a medieval town.

That look was deliberate. The bridge you see was completed in the 1890s, and its builders chose a style called Brick Gothic. This is the red-brick church and town-gate architecture of northern Germany and the Baltic coast, from the Middle Ages. The central towers are often said to take their inspiration from an old town gate tower in Prenzlau, a small town north of Berlin. So a modern railway bridge was dressed up as a fortress. It is a very nineteenth-century idea.

The name has an even older story. Long before this bridge, the Spree here marked the edge of the city. Berlin collected customs duties on goods arriving by water. To control the boats, a heavy tree trunk was laid across the river at night as a barrier. In German, this was the upper tree, or Oberbaum, because it stood at the upstream end of the city. A wooden bridge later took its place, and the name simply stayed.

When the brick bridge opened, it was a symbol of a fast-growing industrial city. Soon after, in the early 1900s, the trains arrived on the upper deck. This was part of Berlin's first elevated and underground railway line. Factories, warehouses and workers' housing spread along both banks. If you imagine this river crowded with barges, cranes and smoke, you are close to how it once looked.

Then came the Second World War. In the final days of fighting in 1945, German troops blew up the central part of the bridge to slow the advancing Soviet army. The bridge was broken in the middle. For years afterwards, it was only patched together. And then the city itself was broken in two.

Here is the first thing many visitors miss. During the division of Berlin, the border did not run down the middle of the river. The whole width of the Spree at this point belonged to East Berlin. The Kreuzberg bank, on the southern side, was West Berlin. So the water itself was a border zone. The bridge became a guarded crossing point, and from the early 1970s, West Berliners could cross here on foot into the East, after controls and paperwork. No trains ran across. The upper deck stood empty for decades.

This border on the water had a painful side. In the 1960s and 1970s, several young children from the Kreuzberg side fell into the river near here and drowned. People on the western bank could see them, but rescuers hesitated to enter water that belonged to the East. These deaths led eventually to an agreement between the two sides about rescues in the border waters. It is a quiet, sad chapter. There is a small memorial to these children on the Kreuzberg bank, close to the bridge.

After the Wall fell in 1989, the bridge had to be made whole again. The repairs took several years. The Spanish architect Santiago Calatrava designed a new central section in steel, which replaced the destroyed brick arches in the middle. Look closely and you can see the difference — the brick on either side, and a lighter, more modern span at the centre. In the mid-1990s, trains returned to the upper deck for the first time since the war.

Now for the second surprise. At night, look up at the arches near the Kreuzberg end. You may see two hands made of neon light, playing rock, paper, scissors. This is an art installation by Thorsten Goldberg. The game never really ends, and nobody wins for long. Many people read it as a comment on the chance and randomness of the old East and West division. It is a small, playful detail, easy to walk past in daylight.

Today, the bridge links Friedrichshain on the north bank with Kreuzberg on the south. These two neighbourhoods were on opposite sides of the Wall, and later they were joined into one city district. Locals have a sense of humour about it. For years, residents of both sides have held a mock battle on or near the bridge, throwing soft vegetables, eggs and water at each other, all for fun. It is part protest, part street party, and very Berlin.

From the middle of the bridge, take a look around. On the Friedrichshain side, a long stretch of the old Wall runs beside the river. It is covered in murals and is known as the East Side Gallery. Further upstream, in the water itself, you may spot a tall aluminium sculpture of three figures, called Molecule Man. And if the bridge looks familiar, it may be from films. It appears in the German film Run Lola Run, among others.

Before you leave, stand at the railing for one more minute. Watch a train cross above you and listen to the rumble fade. Notice the cyclists, the tourists, the locals on their way to work, all moving freely across a place where people once showed papers and waited. The brick is warm in the afternoon light, and the river keeps moving. As you walk off the bridge, whichever bank you choose, you are crossing a line that is no longer there.