City Walls constitute ancient circle of the city and represent the border of its historical center. Built starting from the XIII century and largely still preserved today, they maintain almost original shape despite numerous modifications due to collapses (caused by frequent earthquakes) and urbanistic demolition. They extend for over 5.5 km, incorporating an area of about 157 hectares and following the morphology of the territory along the hill. Original development was slightly reduced over time, with the loss of the walls between Via XX Settembre and Via Roma, which also involved the destruction of part of Porta Barete; other shortcomings are located in Via Castello area and in Viale Collemaggio. Current length makes it one of the most extensive city walls in Italy anyway. Urban gates are characterizing element of City Walls: the four main ones have been realized simultaneously and to these other openings have been followed in correspondence of the main directions with the countryside.