It was conceived in the late 1890s as an innovative transport solution for a developing group of townships then springing up along the River Wupper, in the industrial heartland of North Rhine-Westphalia, Germany.

These towns eventually merged to form the city of Wuppertal in 1930.

The river snaked its way through a narrow valley, and space was already at a premium, so the solution was to build the electric railway following the course of the river, suspended above it.

It opened in 1901, and remains in operation today, as the oldest monorail system in the world, albeit extensively modernised between 1997 and 2004.

It is just over 13km long, suspended 12 meters above the River Wupper, and 8 meters above the city streets. Each working day, 82,000 passengers are carried between its 20 stations in 27 articulated twin units.

I knew none of this when, on my visit to Germany in April 2008, my German friends took me to see it. On Saturday 12 th April, we made the journey to Wuppertal , and my first sight of this railway just took my breath away. A giant steel colossus snaking its way between modern buildings and over city streets.