The city walls of the mighty Kotor fortress, a wonders of mediaeval fortification architecture, were built in phases between the 9th and 19th centuries and represent a complete belt around the old town and the steep cliff of St John's Hill (San Giovani) located above the town. The ring of the wall was completed in the 13th-14th centuries. After the inventions of firearms, new walls were built in front of the old walls. The space in-between was filled with earth and stones.
The total length of the walls is 4.5km, the thickness of the walls is between 2 and 16 metres, and the height is up to 20 metres.
The total length of the main steep route is 1,200m and there are about 1,350 steps