Leonardo draws the entire course of the Arno on two maps: RL 12277 (Windsor Castle), with indication and denomination of its main tributaries; and the Codex Atlanticus, f. 910r, without hydrographic denominations and with only 12 Casentino place names. These maps are remarkable for their precision and for their aesthetic quality. In them Leonardo re-elaborated the traditional layout of the maps by Pietro del Massaio datable between 1456 and 1472.
Leonardo also represents in detail three large areas in the Arno Valley on maps RL 12278 (preceded by RL 12682), 12683 (preceded in part by folio 305r in the Codex Atlanticus and appearing in more detail on folios 52v-53r of Madrid Ms. II) and 12685 (which coincides in part with folios 22v-23r of Madrid Ms. II and with RL 12279). The Arno River starts in the Commune of Stia in Casentino, on the south side of Monte Falterona, in the Tuscan-Romagnolo Apennines, at Capo d'Arno (called the Lake of Idols for the finding there of Etruscan bronze votive statuettes) at an altitude of 1,385 m above sea level.
With a course of 241 km, it traverses, or delimits, the territory of 48 communes in the 4 provinces of Arezzo (Arezzo, Bibbiena, Capolona, Castel Focognano, Castel San Niccolò, Chiusi della Verna, Civitella Val di Chiana, Laterina, Montevarchi, Ortignano Raggiolo, Pergine Valdarno, Poppi, Pratovecchio, San Giovanni Valdarno, Stia, Subbiano, Terranuova Bracciolini), Florence (Bagno a Ripoli, Capraia and Limite, Cerreto Guidi, Empoli, Fiesole, Figline Valdarno, Florence, Fucecchio, Incisa Val d'Arno, Lastra a Signa, Londa, Montelupo Fiorentino, Pelago, Pontassieve, Reggello, Rignano sull'Arno, Scandicci, Signa, Vinci), Prato (Carmignano) and Pisa (Calcinaia, Cascina, Castelfranco di Sotto, Montopoli Val d'Arno, Pisa, Pontedera, San Giuliano Terme, San Miniato, Santa Croce sull'Arno, Santa Maria a Monte, Vicopisano). Its water basin includes 166 communes (160 of them Tuscan).
Leonardo indicates by "La Badiola", the Badia, or Abbey, in the Commune of Collesalvetti.
By "San Savino", Leonardo indicates Badia Sansavino in the Commune of Cascina. The same indication is found on folio 53 r of Madrid Ms. II and folio 305r of the Codex Atlanticus.
Leonardo indicates several times by the name "Calci" the locality to be identified with the famous medieval fortified castle and the Certosa, founded in the first half of the 14th century. By the place name "Val di Calci", mentioned in Madrid Ms. II (22v, 53r), in the Codex Atlanticus (f. 305r) and in the Windsor maps 12683 and 12277, he refers, instead, to the river and the road that traverse the valley known today as Val Graziosa. At the bottom of the valley, at a strategic crossroads, stands what was for Leonardo a reference point for calculating distances (RL 12279): Caprona with its defence tower, indicated also in Madrid Ms. II (ff. 1v, 22v, 53r).
Leonardo represents and indicates the locality of Casciana in the Commune of Lari.
Leonardo represents and indicates "Casciana", today's Casciana Terme.
By Cascina, Leonardo represents and indicates the city's fourteenth-century circle of walls, reference point for the studies and projects for deviating the Arno upstream of Pisa. He also mentions it on folio 305r of the Codex Atlanticus ("Casscina") and on several folios in Madrid Ms. II (1r, 2r, 7v, 16r, 22v, 53r). Particularly significant is the note on folio 7v of the latter codex, with the statement "Here is the view": from Cascina Leonardo studied and drew the Monti Pisani with the Verruca and the fortifications at the foot of the mountain on the other side of the Arno.
Leonardo represents and indicates the locality of "Colle Montanino" in the Commune of Casciana Terme.
Leonardo draws the stronghold of "Colle Salvecti" on the hill surrounded by canals and roads such as the Maremma Road and the Livorno Road. He also indicates the same locality on folio 305r of the Codex Atlanticus.
Leonardo represents and indicates the locality of "Colognole", now in the Commune of Collesalvetti.
By "Foce", Leonardo indicates, on map RL 12683, the tower at the mouth of the Arno (today Bocca d'Arno, near Marina of Pisa). On folios 3r and 52v of Madrid Ms. II he indicates the same locality as "Torre di Foce". It is and again "Foce" on folio 1v of the same Madrid Ms. and on folio 305r of the Codex Atlanticus. The base of this tower still exists today, but incorporated into a building dating from later times in the Torretta locality.
Fossa Nuova e Fossa Reale
Leonardo studies the canals in the plain south of Pisa, and between Ponsacco and Colle Salvetti he indicates by "Fossona" or "Fossana" what will later be the New Canal or Royal Canal.
Fosso Reale Zannone
By "El Zannone" (Alzamone in the traditional reading of Baratta), Leonardo indicates the Zannone Royal Canal. Situated a little to the north of Vicarello, it traverses the Communes of Cascina, Crespina, Lari and Collesalvetti. At the time of Leonardo it was a stream that started from the hill of Lucagnano near Lari and flowed into the dual canals in the vicinity of the Stagno; Leonardo describes it in more detail in Madrid Ms. II, ff. 52v-53r, as "Sannone". Its tributaries were the Crespina and the Orcina.
Castle of Lombard origin and feud of the Della Gherardesca family, of notable strategic importance for Pisa's domination of the Val di Cecina.
By "Monte Vaso", between "Mecocla" and Terricciola, Leonardo indicates the hill amply described by Repetti for its historical and geological importance, "between Val di Fine and Vallecola della Sterza di Lajatico".
Leonardo represents and indicates twice as "Parlasco" the locality of Parlascio in the Commune of Casciana Terme. This place name appears still today twice in very close positions on the IGM maps, confirming the existence of an older Etruscan settlement and of a medieval fortress.
Leonardo represents and indicates several times the city of Pisa as one of the most important centres in his Tuscany, both for biographic reasons (his father Ser Piero had worked there as a notary) and artistic ones. Nor should the city's role from the strategic viewpoint and that of projects be forgotten. It is in fact in relation to the project for deviating the Arno that Pisa appears on maps RL 12683 and 12277, in Madrid Ms. II (ff. 1v and 52r), and in the Codex Atlanticus (ff. 127r and 305r). Leonardo also mentions it for the cathedral and the bell tower on one of the folios removed from Ms. B (Ash. 2037, f. 5v, from the time of his first stay in Milan, c. 1487). And again, around 1515, in relation to a map of the "plain of Pisa" (Codex Atlanticus, f. 225 r). On maps such as RL 12685 and 12279 the position of the city is indicated by a circle, but without place name, since it is clearly recognisable for Leonardo after the bend of Riglione. In Pisa worked and died (1553) Leonardo's nephew, Pier Francesco Da Vinci, known as Pierino, sculptor of the "Dovizia" in Piazza dell'Abbondanza (today's Piazza Cairoli) and of the bas-relief "Cosimo de' Medici driving vice out of Pisa", now in the Vatican Museums.
"Librafatta" is a reference point to the west in Leonardo's project for deviating the Arno. He represents the present-day Ripafratta, in the Commune of San Giuliano Terme, on map RL 12685, and mentions it in the Codex Atlanticus (f. 305r), in Madrid Ms. II (f. 52v) and in RL 12683. This stronghold was fundamental for controlling the valley of the Serchio and notably important also in relation to the Verruca.
San Benedetto a Settimo
By "Settimo", Leonardo indicates the 7th mile from Pisa, and more precisely, San Benedetto a Settimo, in the Commune of Cascina, on map RL 12683 and on folio 305r of the Codex Atlanticus. In the traditional Vincian transcriptions, Settimo was joined to San Savino, although they are two different localities.
Leonardo represents and indicates the church of San Jacopo, in the Commune of San Giuliano Terme, on map RL 12683 and mentions it in Madrid Ms. II (f. 52v) and in the Codex Atlanticus (f. 305r).
San Piero a Grado
By "San Piero in Grado", Leonardo indicates the Romanesque Basilica of San Piero a Grado (in the Commune of Pisa), a place of early Christian worship, frescoed by the painter from Lucca Deodato Orlandi. Leonardo mentions it also on folio 52v of Madrid Ms. II. It occupies a strategic position for controlling the Arno, as demonstrated by the decision of the Florentines to construct an "entrenched field" in this place during their sieges of Pisa.
Leonardo represents and indicates the locality of San Regolo in the Commune of Fauglia.
By "Via of Maremma", Leonardo indicates today's State Road 206, which connected Pisa to Collesalvetti.
Leonardo draws and indicates Tremoleto in the locality of Lorenzana.
Uliveto Terme (Bagno)
Leonardo takes an interest in thermal centres, which he often indicates as "Bagno". With this place name in RL 12683 he probably intends to indicate Uliveto Terme, while in Madrid Ms. II (f. 52v) it presumably refers to San Giuliano Terme. In RL 12685 and in the Madrid Ms. (f. 23r) the same word is used instead to indicate Montecatini Terme.
Verruca (Fortezza e Monte)
Leonardo indicates by "Verruchola" (or "Verrucha") the strategic fortress and the mountain of Verruca in the Commune of Calci. He draws on Madrid Ms. II and on Windsor paper RL 12683; and also mentions it on the Codex Atlanticus. The place is perhaps evoked in idealised form also in a drawing of an "Apocalyptic flood" dating from around 1516 (Windsor, RL 12385). On June 2, 1503 that Leonardo went to inspect the fortress, reconquered by the Florentine Republic, to plan its restoration.
Leonardo indicates Vicopisano ("Vico") on map RL 12279, in Madrid Ms. II (ff. 2r, 22v, 53r), in the Codex Atlanticus (f. 305r) and represents it, without specifying the name, on map RL 12683. In stenographic synthesis, he evidences the fortifications of Vicopisano with the great tower attributed to Filippo Brunelleschi. in the wars between Florence, Pisa and Lucca, this stronghold occupied an exceptional strategic position, being much closer to the Arno in the past.