The city walls of Capalbio are the ancient defensive ring of walls of the village. The first city wall is of medieval origin, built between the 11th and 12 centuries and commissioned by the Aldobrandeschi. Its purpose was defence and sighting over the surroundings of the Capalbio Fortress, then the center of feudal power. The walls were modified in the 15th century under the Republic of Siena, who built a second ring, higher than the first.
A series of towers, most of which have a square base, intersperse the walls. There are also sections of scarp basement on the outer side and crowning battlements. Some portions of the walls coincide with the outer walls of other buildings.
Because of the different height of the two walls the double walkway is particularly unusual, but it offers an amazing panoramic view.
There are also two lateral gates: the main one is Porta Senese, which bears a plaque from 1418 to commemorate the restructuring of the walls and the Medici coat of arms from 1601, when Capalbio was annexed to the Grand Duchy of Tuscany.