Rosie Goldsmith goes underground in Berlin, searching out the men and women involved in reunifying the city below street level, examining how the tubes, telephone, water and electricity systems of east and west were reconnected after the fall of the Wall.
When the Berlin Wall fell in November 1989, the world saw images of ecstatic Berliners celebrating a new freedom of movement across their city. But after the jubilation had died down, council chiefs were faced with a task without precedent in any city in the world. Public transport in the two halves of the city was in chaos and the main arteries of Berlin became clogged with polluting Trabants; using the telephone was an infuriating experience; utility companies faced similar problems trying to bring together two systems which had developed completely separately.
The great symbolism of the fall of communism had been replaced by a more practical but no less crucial question - how to reunite the infrastructure and fabric of a vast city that had been divided for nearly 30 years.
Rosie speaks to the key figures involved in the hugely costly task of restitching the city - among them former West Berlin mayor Walter Momper - as well as ordinary Berliners who recall everyday life in the city after the fall of the Wall. City officials knew that rebuilding their infrastructure was vital to making citizens feel that they were part of a city - and a country - that was physically as well as symbolically reunited.
Rosie Goldsmith looks at how the infrastructure of Berlin was reunited after the Wall fell