Valdichiana

Once it had withdrawn, in the upper Villafranchiano (about two million years ago) central Italy hosted large lakes, including that of the Chiana basin which was short-lived as it was drained (at the beginning of the Pleistocene) by the erosion of the hilly threshold of its waters, to take the form of a canyon crossed by a river, tributary of the waters of Lake Trasimeno (whose formation ended 110,000 years ago).

Its valley floor was very hollow in the centre, with a "V" shape due to western tectonic extension, eastern compression and progressive erosion determined by the transit of water towards the south, as evidenced by core samples and geological studies, even recent ones, and was furrowed by the so-called "Arno Tiberino" before that its waters were captured by the current riverbed towards Incisa and Florence.

Human interventions have made the valley floor totally flat, between San Zeno (Arezzo) and Parrano (in the province of Terni), as well as raising the valley floor itself by several metres, making the Chiusi Scalo area the highest in the Val di Chiana with 250 mt s.l.v., with almost "zero" slope of the waters and with very high hydraulic and hydrogeological risks.

After the flooding of the Clanis Valley caused by a gigantic dam in 1052-1055, built on the orders of the Holy Roman Emperor and the German Pope Leo IX in the Orvieto area (located near the castle of Carnaiola), in 1338 the Republic of Florence ordered the people of Arezzo (just subdued) to build an artificial canal to drain the waters of the large artificial lake (so-called Chiana) towards the Arno, dug into the rock.

This canal was initially 400 meters long, but the Republic of Florence ordered its extension, so as to drain ever greater quantities of water, drainage which however was hindered by the milling industry of the powerful Arezzo Monastery of Ss.

The beauty of the valley (whose waters flowed naturally from Arezzo to the Tiber) and the excellent farming activity was mentioned by Pliny the Elder in his Naturalis Historia (Book III, 52-54).

Goethe a few centuries later wrote about Valdichiana in his Italian Journey: "Fields of such beauty are impossible to find elsewhere; every lump of earth has been tilled to perfection, prepared for sowing.