Porta San Donato belongs to the third and last circle of the walls of Bologna. It was built in the thirteenth century to defend the road to the valleys of Argenta and Ferrara, it was transformed in the fifteenth century and it still retains the old forepart or "rivellino". Porta San Donato stands on the ancient via San Donato (or via Zamboni in the section within the walls), which connects Bologna to the Bolognese countryside in the north-east. It was first built in the 13th century. Made of brick, next to it were the lodgings for the guards. On the same eastern side, not far to the south, a door called San Giacomo was originally opened, which was later blocked in the 14th century. In 1354, a drawbridge was built. Closed and reopened several times, between 1952 and 1959 it was demolished more than a meter of walls to allow a better flow of vehicles from the avenues in Via San Donato.