Originating in Siberia, the Forest quickly began to conquer new territory, inexorably spreading around the world. It relentlessly moved from the East to the West, absorbing the remains of human civilization. Despite all efforts, the government could not cope with the Forest and soon fell under its onslaught. Only natural barriers could halt the spread of the Forest.
One of such barriers was the Rhine River that divides the Western Europe from the Alps to the North Sea. For some time, the combined forces of Europe managed to restrain the Forest. Most of the Rhine bridges were destroyed. It was decided to keep safe at least one bridge in each large city so that survivors could move to a secure territory.
The powerful defensive structures successfully performed their duty but any kind of defense would be breached sooner or later. The Rhine frontier was no exception. Eventually the Forest found a way to overcome it, fully capturing Europe. Once surrounded, the defenders of the Cologne bridge continued to fight back thereby making the bridge a shelter for hundreds of survivors.
The struggle for life continued for several years. Over this period an entire city was built on the bridge. But the defenders grew smaller in numbers and it was obvious that the Forest would be able to capture their enclave - it was only a matter of time. Unfortunately, the further fate of the survivors is unknown. For some reason the inhabitants had left the Cologne bridge leaving their settlement to be devoured by the forces of nature.