Siena is located on a hilltop of porous, shoreface, Pliocene sandstone. It became an important town in medieval times (1100-1400 AD) because it was on a major route for pilgrims travelling from France to Rome the Via Francigena. It suffered from an absence of readily available water because no large river flows nearby. It was also involved in continuous fights with neighbouring Florence and the territory was not readily defendable. The solution for the medieval town was to build an underground aqueduct consisting of a 25 km-long network of tunnels, called Bottini, which collected water from hills to the northwest and brought it to public fountains (fonti). The underground aqueduct was used for drinking water until the early 1920s. It is now being refurbished to provide water for general use and particularly for watering gardens and city parks.

The objectives of the field trip are to examine the geomorphology and geology to determine the main characteristics of the aquifer (shore sandstones and conglomerates), aquifuge (offshore and lagoonal silty clays), and water potential of the area; to consider the historical-sociological conditions that led to the construction of the underground aqueduct; to marvel at some of the engineering and architectural constructions of the aqueduct itself and at the monumental fountains; and, finally, to savor, albeit briefly, the enchanting atmosphere, architecture and cuisine of Siena, one of the best preserved medieval towns of Tuscany, in both its buildings and way of life.