Treviso is enclosed by a complete circuit of Renaissance walls built between 1509 and 1518 by the Republic of Venice, designed by Fra' Giocondo. The walls are low and broad in the Italian bastion style — angled for cannon defence rather than height — and three of the original gates still stand: Porta San Tommaso to the north, Porta Santi Quaranta to the west, and Porta Altinia to the south.
The path along the top of the wall is mostly accessible and gives an excellent quick orientation to the city. Porta San Tommaso is the most decorated, with carvings of the lion of Saint Mark and an inscription from 1518.