The city walls are the medieval defensive mechanism surrounding the old city of Nuremberg, Germany. Construction started in the 12th Century and ended officially in the 16th Century. They measured 5 kilometers (with about 4 kilometers still standing) around the old town. The Nuremberg Castle together with the city wall is meant to be one of Europe's most considerable medieval defensive systems. The city wall is one of the most important art and architectural monuments in the city of Nuremberg. In the north, the extensive castle complex is fully integrated into the fortification.