Berlin's U-Bahn is an intriguing underground journey of spectacular design

Twenty-five years has passed since the fall of the Berlin Wall, the symbol of the Cold War. Now the wall has almost completely gone, just like so many other historical monuments from Berlin's dark past, it's often difficult to get a sense of what once was. But perhaps one of the best places where you can still sense the history of Berlin, is within the city's underground subway known as the U-Bahn.

Danish Photographer Patrick Kauffmann has captured the U-Bahn's architectural diversity and spectacular design, which offers an intriguing journey of colour, form, pattern and typography. No two of the 173 stations are alike, because the network has continued to develop and expand over the past 100 years, with the most recent station opening in 2009.

Kauffmann explained: "In the U-Bahn you can experience a sway of different time eras and styles ranging from Art Nouveau and Art Deco over German Jugenstile and Bauhaus to the Futurism of the 1970s. Also very different ideologies are represented here, most notably from the Cold War era, where Berlin was divided into Eastern and Western parts.

"Even when the wall was constructed, West Germany was allowed to use some of the underground network, against a generous payment to East Germany. Hereby emerged the 'Geisterbahnhöfe' or ghost stations, where East German border guards would patrol the dimly-lit platforms, while the U-Bahn train from West drove past, not allowing anyone to get off or on the carriages.

"An era which is not present in the U-Bahn is the Nazi era, where the U-Bahn tunnels were primarily used as bomb shelters. However, a few remains are to be found here and there, for instance at U-Bahn station Mohrenstraße, where the red marble is recycled from Hitler's Reich Chancellor Building."