Leonardo took an interest in Val di Chiana, which had been named in ancient times for the river Clanis, a tributary of the Tiber, especially during the years 1502-1503, at the time of Cesare Borgia. This area, occupied in the Middle Ages by a swamp extending nearly 40 km, mentioned also by Dante in the Inferno, was subjected, starting from 1342, to a number of land reclamation initiatives conducted by Arezzo and Florence, attempting to drain the waters into the Arno by digging a master canal which, during the Grand Duchy of Tuscany, reached as far as the Lake Montepulciano. In Leonardo's time the Palude, or swamp, began at Ponte alla Nave and extended, after Ponte a Vaiano, as far as Ponte a Beccatiquello; on map RL 12278 (Windsor Castle), the relationship between the marshlands and the watercourses that flowed into them is evident. Significant on map RL 12277 is the note «Braccio da Montone closed it where necessary», referring to the channeling underground of a canal that connected the Chiana to the Lake of Perugia, that is, Lake Trasimeno. Leonardo's studies in this zone are extremely thorough. Shown on map RL 12682 are the distances between the two chains of hills that bound the valley to the east (Castiglion Fiorentino, Montecchio, Cortona,...) and to the west (Foiano della Chiana, Lucignano, …) as well as indication of the route from Arezzo to Cortona in the direction of Perugia; on map RL 12278 instead, the itinerary leading to Foiano della Chiana through Ponte a Pietra is described.
Battifolle • Calcione • Castiglion Fiorentino • Cesa • Chiana (river) • Chianciano Terme • Chiani • Chiusi • Ciggiano • Cilone (torrent) • Civitella in Valdichiana • Contignano • Cortona • Foiano della Chiana • Gargonza • I Ponti • Lucignano • Mammi • Marciano • Monte San Savino • Montecchio • Montepulciano • Pierle • Poggiola • Ponte a Chiani • Ponte alla Nave • Renello • Rigomagno • Santa Maria alla Poggiola • Torre Beccati • Valiano • Vingone (torrent)