I Bottini - The medieval Acqueduct of Siena - The ancient water supplying system related to the urban, social and economic development of Siena, Water Forum, Kyoto (Japan), p.74-75,16/3/2003 -17/3/2003

One of the most beautiful cities in Tuscany, Siena is still characterized by the same architectonic and urban features as in medieval times. As a result Siena city centre has been granted UNESCO World Heritage status. Despite its unique territorial context and setting, Siena is located in one of the worst irrigated uplands in Tuscany. The topography of Siena is strictly linked to the geological and morphological features of the area. The hill on which the city stands is formed of an impermeable clay ‘base’ over which a permeable layer of sandstone, shoreface sands and Pliocene marine conglomerates has been deposited. The hilly landscape owes its shape to erosion, which has dug deep valleys and brought the underlying clay to the surface. These valleys collect the waters which flow in the springs naturally arising in the lower slopes of the hill, a hydrogeological scenario which, together with the fact that the city of Siena lies near the top of the hill, has made water provisioning in the area a particularly challenging task. Siena is built over an existing Etruscan-Roman settlement whose centre lay on the San Quirico hill until the Late Middle Ages. The ancient city took its name - Castelvecchio – from the first castrum, the residence of the bishop, to be built there. The modest amount of water needed by this settlement was supplied by an underground aqueduct dug in Roman times (perhaps following the route of an existing Etruscan system). This aqueduct was severely damaged during the centuries following the fall of the Empire and there remains no direct evidence of its existence. However it is not difficult to imagine that the underground tunnels into which rainwater and small springs flowed in the Classical age were the same channels which, with some alterations, supplied the fountains at the foot of Castelvecchio in the Late Middle Ages. Close examination of the layout of the oldest fountains in the city of Siena shows that they are located (low down and often dug into the hill) all around the area originally covered by the ancient medieval settlement. For example the ancient Fontanella water fountain is located just below the medieval settlement at the foot of a steep slope. The ceiling of the underground aqueduct which feeds this fountain is vaulted in the Etruscan style, while the walls are unlined. As a result the inside of the tunnel is coated with limescale. The effect is beautiful but must have caused serious problems for those who needed limpid water, free from calcite.