Landscape influence on the development of the medieval city-state of Siena, Italy

This paper examines how the landscape has influenced the development of the medieval–early Renaissance city-state of Siena, Italy. Siena is a hill-top town with a historic ~2 km2 wide core surrounded by ancient city walls. It still preserves the medieval urban plan and Gothic architecture, and its inhabitants keep ancient traditions alive. It is built on Pliocene, loosely cemented, calcareous, marine, porous sandstone that overlies impermeable marine calcareous silty clay. The town is limited on three sides by steep slopes indented by secondary deep, narrow, small valleys. The forth side to the north is a gently sloping terrain along the hilltop leading to distant highlands. This geomorphologic setting had been beneficial to the development of the town during mediaeval times because readily defendable and, being far from wet, unhealthy, malaria-infested lowlands, it was crossed by a major medieval pilgrimage route (Via Francigena) to Rome. However the hilltop location presented difficulties such as scarce availability of water and limited space to expand. Siena tried valiantly to adapt to the demand of expanding population and international markets. Two major underground aqueducts were built for a total of about 25 km long tunnels, to bring water both to the centre of the walled town mainly for human consumption and to a major fountain (fonte) complex at the base of the hill that was the major medieval industrial site. However, water was never plentiful and became totally insufficient for the expanded mechanized industrialization of cloth-making that started in mid 14th century. Siena could not compete with other towns, like the neighbouring Florence, endowed with fluvial hydraulic power. Like other hill-towns Siena also had the problem of limited space for its growing population inside city walls. Within the city the space was and still is maximized in two main ways. One is to level hilltops for constructions, such as the Cathedral, or cut terraces into the easily quarried soft sandstone for buildings. The other is to build retaining walls in the upper parts of the secondary, indenting, narrow valleys and partially filing their apex, as it was done during the last century to obtain the stadium and associated athletic facilities, or, in the medieval times, to build the famous Palazzo Pubblico (Town Hall) and its antecedent, sloping semi-arcuate (Pecten-shell like) public square.