Leonardo refers to Castelfranco in the Codex Madrid II on folios 1r, 2r, 3r and 22v and on maps RL 12279 and RL 12683, which however lack any place names.
Castelfranco was created around the 11th century by the unification of San Bartolomeo a Paterno, San Michele in Carpugnana, San Piero a Vigesimo and San Martino in Catiana, four small villages which are described by the canon Giovanni Franceschini (1789) as the distinguishing feature of the territory before the construction of the castle.
The defensive wall that surrounded the historic centre was dismantled during the 1960s and only four city gates remain standing.
Cerreto is important in relation to Leonardo for at least six reasons: the legend that his mother was born in the stronghold of Cerreto, in a house situated on the ancient ramp of stairs that led to the Pieve di San Leonardo; the property documented as having been owned by his father Ser Piero at San Zio di Cerreto Guidi; the double stairway of the Medicean Villa, which recalls those found in Leonardo's Ms. B; its location close to Vinci, dominating the thoroughfares of communication between the Arno and the Padule di Fucecchio, between the course of the Vincio and that of the Streda; its historic connections with Vinci, from the time of the Guidi Counts (11th century) to the Podesterate of Vinci and Cerreto; the Della Robbia baptistery in the Pieve di San Leonardo, with a formella inspired by Leonardo's drawing dated 1473 and by the "Baptism" in the Uffizi. We find Cerreto not only on map RL 12685 (Windsor Castle), but also on 3 folios in Madrid Ms. II (ff. 2r, 3r, 23r): on the route from Vinci to Vicopisano, in the surveys and the diagram of a project for deviating the Arno through Prato and Pistoia.
A centre of art, commerce and communication, Empoli was important for Leonardo's formation. He represents and indicates the fortified city on maps RL 12278 and 12685. He also mentions it in Madrid Ms. II (ff. 2r, 16r, 23r) in connection with the project for deviating the Arno; on the route from Florence to Pisa, and in particular from Empoli to Cascina, with the relevant distances. In the Collegiate and its Museum are important works by Masolino, Rossellino, Mino da Fiesole, Filippo Lippi, Botticini and Andrea Della Robbia.
A stronghold on the ancient Via Francigena, Fucecchio was a strategic point in the medieval road system, and for crossing the Arno in particular. It was located in proximity to the confluence of the waters of the Padule di Fucecchio (and thus to Leonardo's Arno Canal project) with the navigable Arno. Leonardo represents and mentions it on maps RL 12685, 12277, 12279 (Windsor Castle)and on three folios in Madrid Ms. II (1r, 2r, 23r).
Lastra a Signa
By "La Lasstra" Leonardo indicates Lastra a Signa, a centre of roadways as well as cultural and commercial activity in the Arno Valley. It is located on the route from Florence to Empoli, almost at the height of Ponte a Signa, the bridge that in the past joined the left bank of the Arno to the stronghold of Signa, in proximity to the weir and the river port called Porto di Mezzo, upstream of Golfolina. Leonardo indicates "La Lastra" on the maps and calculations for deviating the Arno (RL 12685 and Madrid Ms. II, ff. 7r, 15r, 16r; on f. 23r he shows it, instead, without naming it).
Leonardo represents and indicates Malmantile on maps RL 12278, 12685, 12279 (Windsor Castle), in Madrid Ms. II (f. 23r); he also mentions it in Madrid Ms. II (ff. 3r, 16r). The stronghold, whose construction was probably supervised by Brunelleschi, is located in the Commune of Lastra a Signa, along one of the roads that led from Florence to Montelupo Fiorentino and then to Vinci. A tradition no longer accredited (in spite of the presence of a church dedicated to Our Lady of the Snow) identified it as the stronghold appearing in Leonardo's drawing dated "the day of Our Lady of the Snow, 5 August 1473".
Leonardo is interested in Montelupo for at least four reasons: as a production centre of artistic ceramics (with important masters and prominent clients), for its thoroughfares of communication, for his studies on the Arno valley and the Val di Pesa, and for his observations on the conformation of the terrain. On the maps for deviating the Arno into the Pistoia Canal, around 1503, he draws it on RL 12685 (Windsor Castle); indicates it on maps RL 12278 and 12279 (Windsor Castle), and in Madrid Ms. II (folios 3r, 15r, 16r, 23r). Leonardo was well acquainted with the kilns of Montelupo (15 kilometres from Vinci), as is confirmed by the itinerary on folio 15r of Madrid Ms. II from Signa to "Monisterio, Pescaia, Fornaci, Montelupo". This is an annotation dating from the years in which "moresca" (Moorish) majolica decorated with intertwined patterns resembling the "Vincian knots" was produced at Montelupo. Other mentions of the town are found in the Codex Atlanticus, on folio 201v, dating from 1505-1506: "How the beds of river rise with the passage of tme toward the surface of the water, as shown by the Arno that runs from Monte Lupo down, where once there was sea, and before it did not run ". And in the Codex Leicester (c. 1506-1508), on folio 6A-31v: "... and the Arno is similar, at Monte Albano, around Monte Lupo and Capraia, where the great boulders and are all made of agglomerated pebbles, of different stones and colours"; and on folio 8B-8v: "Near where the rivers fell tino the sea at great depth, like the Arno, which fell at Golfolina near Monte Lupo, and left there the pebbles which, as can still be seen, have formed a single agglomeration made up of stones of various countries, kinds, colours and degrees of hardness…".
By 'Pontormo', Leonardo represents and indicates the stronghold of Pontorme, on maps RL 12278 and RL 12685 (Windsor Castle), in the Commune and at the gates of Empoli, on the road to Montelupo. It was a centre of ceramics production, as well as the birthplace of Pontormo.
Leonardo represents and indicates the stronghold of San Romano, in the Commune of Montopoli in Val d'Arno, on map RL 12683 (Windsor Castle) and mentions it also in Madrid Ms. II (f. 16r, as "Torre a San Romano" and f. 22v).
On the right bank of the Arno, Leonardo represents the stronghold of Santa Croce sull'Arno without indicating its name. He thus marks the beginning of the Pisan territory subject of his reconnoitering. Santa Croce appears also on other Leonardo folios: in Madrid Ms. II (ff. 2r, 3r, 22v-23r) and on map RL 12279 (Windsor Castle) .
Signa was a centre of art, crafts and communication occupying a strategic position near the Ombrone Pistoiese dominating the confluence of the Bisenzio with the Arno, at the height of the river port - where goods from Pisa arrived - and the bridge over which the river could be crossed. Leonardo represents it on map RL 12685 (Windsor Castle) and mentions it in other studies on the course of the Arno and for its deviation, in the itinerary between Florence and Empoli-Pisa (RL 12279, the Codex Atlanticus and Madrid Ms. II).