The Valdichiana, whose name derives from the river Clanis (today's Chiana), is mentioned as the Clanis Aretinum basin by Pliny the Elder is his Historia Naturalis. The watercourse received waters from Casentino and from numerous torrents that gradually turned a vast area into swampland. The Etruscans carried out the first initiatives aimed at regulating the waters in the area to make the land arable and the Chiana River navigable down to the Tiber. The valley was long considered so fertile and productive that it was still known as the "granary of Etruria" in Roman times. The Romans continued the work in the valley, building fish-weirs along the course of the Chiana to improve the fishing conditions and make the area more wholesome. The Valley was also involved in the building of the Cassia military road, which crossed it longitudinally. The last years of the Republic saw the beginning of a slow decline, during which the whole area became swampland, due also to the progressive inversion of the course of the Chiana from the Tiber to the Arno. Between the 10th and the 13th centuries, isolated attempts at draining the swamps were made by the monks, who had only inadequate means. The most important initiative was the construction of the Chiusa dei Monaci (Monks' Dam) in 1151. In the 13th century the place became insalubrious and desolate, and as such it is recorded by Dante Alighieri in the Divine Comedy (Inferno - XXIX, 46-47; Paradise -XIII, 23).

In 1338 the government of Arezzo launched an attempt at land reclamation that called for the construction of the Fossatum Novum, a longitudinal canal of about six kilometers. In 1492 the Papal State and the Florentines discussed other projects, not implemented due to the opposition of Siena. Between 1502 and 1503, Leonardo Da Vinci drew up, at the order of Cesare Borgia (Il Valentino), a study for hydraulic works in the territory that called for the construction of a navigable canal along the Arno down to Pisa; famous is his birds' eye view of the Valdichiana (Windsor Castle, Royal Library, no. 12278). In 1551 Cosimo I de' Medici commissioned the engineer Antonio Ricasoli to make a thorough survey. A general land reclamation project would be possible only when all of the territories had been brought under Medicean power. Under Ferdinand I a systematic initiative of draining the swamps began and the first great grand-ducal farms were built on the reclaimed land. Later, projects were requested even of Galileo Galilei, Vincenzo Viviani and Evangelista Torricelli. In particular, Torricelli, who had strongly opposed the project of Andrea Gaci from Castiglione, drew up a hydrodynamic plan, which was not implemented, in which he declared the filling-in method to be the only suitable means for land reclamation in the valley.

After several minor initiatives, work resumed under the reign of Grand Duke Peter Leopold of Lorraine who, in 1763, commissioned Leonardo Ximenes to draw up a project for land reclamation in the area. The project was not implemented due to the opposition of the mathematician Tommaso Perelli, who was in turn to plan and carry out an initiative of his own. Between 1789 and 1827 it was the turn of Vittorio Fossombroni, who planned to give a regular slope to the valley by means of filling-in and to govern the course of the streams and rivers. The work was then put under the direction of the Florentine engineer Alessandro Manetti who, from 1838 to 1859, planned and carried out numerous initiatives, among them the realization of a basin with an artificial waterfall six meters high. After the Unification of Italy, further initiatives were carried out by Carlo Possenti, inspector of the Arezzo Civil Engineers Corps, who completed, with some modifications, the work begun by Manetti. By the 1930s, land reclamation could be considered completed.

Some buildings dating from the land reclamation period are of great interest. Beautiful, for example, is the imposing estate of Rugliano, built in the 18th century over an earlier Roman construction. It can be visited along a fascinating itinerary that leads from Pieve al Toppo to Viciomaggio on the Siena-Arezzo State Road 73.