Windsor Castle, RL 12683

His interest in the sea and in ports had brought Leonardo to Livorno already prior to 1480. His studies were focused, in particular, on the projects for deviating the Arno upstream of Pisa, toward the Stagno di Livorno (culminating in 1503-1504), and on the fortifications of Piombino (around 1502 for Cesare Borgia, in 1504 for Jacopo IV Appiani).
The care taken by Leonardo in the surveys of this territory is especially apparent on map RL 12683 (Windsor Castle) and on folios 52v-53r of Madrid Ms. II.

The Lucchesia (territory of Luca), especially the areas around Montecarlo and Altopascio, is involved in the projects for deviating the Arno in the preliminary sketch of 1495 and on the maps of 1503-1504 (RL 12685, RL 12683 and Madrid Ms. II, 22v-23r). Obviously, Lucca is clearly evidenced both as an important city of art and because it was the object of a singular project for flooding the city, devised to facilitate its conquest (Ms. B, f. 64r, around 1487).
The itinerary, with measurement of the distances, that starts at Poggio a Caiano and Montale and, passing beyond Pistoia, arrives at San Gennaro and Villa Basilica, is traced in Madrid Ms. II.
On map RL 12277 Leonardo traces the course of the Serchio, while on RL 12685 he represents only the town of Barga.

This broad territory traversed by the Arno river was systematically scoured by Leonardo along the routes between Florence, Vinci, Empoli and Pisa. His reconnaissance was not limited to a route running along the two banks of the river, but was extended to the surrounding hills, all accurately indicated and measured on numerous maps (RL 12277, RL 12278, RL 12685, Madrid II: ff. 22v-23r, 53r, 2r, 15r, 16r).
This route connects without a break to those routes and geographic areas that, proceeding along the Arno from upstream to downstream, are indicated on maps RL 12278 and RL 12685 as "Florence and surroundings", "Prato-Pistoia", "Val di Pesa and Val di Greve", "Montalbano", "Valdelsa", "Volterrano and Valdera", "Pisa and surroundings". Leonardo traversed these places innumerable times, from childhood to his second Florentine period (1508), and probably again at the time of his departure for France (1516). In addition, this territory was at the centre of his studies pertinent to the projects for deviating the Arno: for the Florence Canal (at least from 1473 to 1513) and for the Canal leading to the Stagno di Livorno (around 1503-1504).

During the first years of Leonardo's career, his father Ser Piero worked as notary in Pisa.
Leonardo studied the localities, watercourses and mountains in the territory of Pisa, especially during the years 1503-1504, for his project for deviating the Arno toward the Stagno di Livorno, the realisation of which was begun on August 22, 1504, only to conclude in failure the following autumn. The detailed cartography of this territory is found in RL 12683 (for the southern part), in Madrid Ms. II (on f. 22v, and especially on ff. 52v-53r; with routes and calculations on folios 1r, 1v, 2r, 3r, 16r and landscape on folios 4r, 7v e 8r) and in the Codex Atlanticus (307r).

Map RL 12278 and above all RL 12683 (Windsor Castle) show how this zone, around 1502-1504, held great strategic importance for Leonardo, being involved in the Florentine military campaign to recapture Pisa (which had become independent at the time of the incursion into Italy of Charles VIII, King of France) and thus to the project for deviating the Arno away from the rebellious city. Leonardo's reconnaissance of the territory was not, however, entirely systematic, especially as regards the territories farthest away from the course of the Era, and this fact explains the presence of irrefutable errors in the positioning of some localities, as in the case of the Terricciola area.

On maps RL 12277, RL 12278 and RL 12683 (Windsor Castle), great importance is conferred on the city of Volterra, located between Val di Cecina and Valdera; a center of historic-artistic interest, Volterra had in fact, since antiquity, played an important strategic role, both for its position within the Tuscan system of roadways and for the mining resources in its territory. Evidently, Leonardo traversed its territory while serving under Cesare Borgia and at the time of the war waged by Florence against Pisa (around 1503), but conducting non-systematic reconnaissance justified by his fragmented knowledge of the area.