During a period of peace between the city factions and guilds was begun the great new walled enclosure. Was the year 1284 when the walls were planned with the consultant of the architect Arnolfo di Cambio. The real works started only in 1298 and proceeded slowly and irregularly.
First were build the main gates (Porta La Croce, Porta San Gallo, Porta al Prato) linked together with temporary defences in earth and timber. Piece by piece the wall grew up, the work was accelerated in 1311 fearing an attack of Henry VII’s troops. When finished, in 1333, the Florence’s new walls were a great spectacle! Here some records and data: the perimeter was about 8,5 kilometres long, the walls were about 12 meters high, 2 meters width and entirely crenellated with Guelph battlements, endowed with 73 tower, one each 115 meters rising up to 23 meters, other towers flanked the 16 small and great gates. In 1324 the curtain was reinforced with ditches and bastions. The whole area enclosed was 630 hectares, against the only 80 of the previous walls. These walls were in practice an expansion of the fifth enclosure because the streets of new suburbs followed the previous ones that broke away from the Roman nucleus. The sixth enclosure was able for a long time to contain the whole city. The reason were two: first, the constructors had well understood the errors of their predecessors; second, no one had the possibility to foreseen what happened in less than 20 years in the whole Europe: the coming of Black Plague Death.
So the new walls were for centuries oversized, great areas destined to urbanization remained green and here found place the magnificent Renaissance gardens. However, the project of the new walls was very well carried out: the opening of new roads, the demolition of narrow alleys, the construction of the ‘Lungarni’ (roads running along the banks of the river) and many other roads, the new discipline for stagnant water and hygiene: Florence, one of the greatest cities of the Early Middle Age, anticipated some of the problems typical of the modern age.
In the last century, restructuring brought the city to be the capital of the Kingdom of Italy and the city walls were demolished, with the exclusion of the gates. The entire line on the right bank of the Arno was replaced with the actual Avenues of circumrotation. The man responsible of this havoc was the ‘great’ architect Giuseppe Poggi. But now is time to have a look on the other side of the river, the left bank, with great part of the sixth enclosure fortunately still intact!