The transition to communal forms of government, the victorious struggles against the feudal lords of the county, the success of productive activities such as the processing of wool, and of commercial and banking enterprises with an ever-increasing reach, organised in increasingly influential guilds, triggered a period of great political, economic and social development between the twelfth and thirteenth centuries. Indeed, by the mid-thirteenth century, Florence was one of the most populous cities in Europe and a major economic centre, despite the clashes between the Guelph and Ghibelline factions into which the local aristocracy was divided.
The process of saturating the vacant spaces between the older circle of walls and the twelfth-century wall took place rapidly, and very soon development overtook even the new walled circuit. This tumultuous expansion clearly distinguishes the ‘old town’, enclosed within the late antique walls, from the ‘new town’, enlarged outside them. Clear aesthetic aspirations also emerged in the urban projects, the result of the new inclination towards regularity and rationality, considered essential conditions for achieving the beauty that was increasingly mentioned in the documents of the time.
The city developed by combining the straight lines of the hamlets with the structuring presence of a series of new focal points, mostly made up of the churches and convents of the mendicant orders, around which the life and growth of entire urban sectors were concentrated. The settlement in Florence of these orders took place in rapid succession: the Dominicans arrived in 1221 at Santa Maria Novella, the Franciscans before 1228 at Santa Croce, in 1250 the Servites at Santissima Annunziata and the Augustinians at Santo Spirito, the Humiliati in 1251 at Ognissanti, the Saccati at Sant’Egidio in 1259, the Carmelites at Santa Maria del Carmine in 1268. The friars settled outside the walls in the twelfth century, around small churches that were later rebuilt to form large monastic complexes. Often, the development also drew in the surrounding land, acquired or donated by benefactors, which was urbanised with rows of simple houses, populated by the new inhabitants who came to the city from the countryside. With their uniformity, and despite additions and alterations, these rows of houses still characterise many streets outside the twelth-century circle.
In the areas of new expansion, an urban design was applied that was no longer based on an orthogonal grid of streets and lanes, as in the old part of the city, but on wide, straight roads that directly connected the main centres and road junctions, creating unprecedented solutions, such as the convergence of several streets into a two or three-way fork. Large squares were then opened in front of the new churches of the mendicant orders, often with the contribution of the municipality, forming the first large public spaces in the city after those destined for the market.
In the vast lands to the north of the circle of walls – the so-called ‘Campus Regis’ and Cafaggio – parcelling of land was arranged by the episcopate or private individuals starting from existing routes, such as the road of Borgo S. Lorenzo and that of Campo Corbolino (today’s Via Faenza); or by laying out new rectilinear streets, forming a very wide-meshed road network with large internal green spaces.
Urban growth also concerned the Oltrarno, which by the twelfth and thirteenth centuries was an integral part of the city, thanks in part to the construction of three new bridges: the one at Carraia (begun in 1218), at the western end of the new walls, the one at Rubaconte (1237), in a symmetrical position compared to the previous one, and finally the one at Santa Trinita (1252), from which a new straight line – the ‘Via Maggiore’ or ‘Maggio’ – was started, heralding the full urbanisation of the western part of the Oltrarno, gathered around the churches of San Frediano, Santo Spirito and the Carmine.