Crete Senesi is a term for an area of Tuscany in Italy, immediately to the south and east of the city of Siena. It consists of a range of rolling hills and woods among villages and includes the communes of Asciano, Buonconvento, Monteroni d’Arbia, Rapolano Terme, and San Giovanni d’Asso, all within the province of Siena. They border to the north with the Chianti Senesi area (see Chianti Colli Senesi DOCG), to the east with the Val di Chiana (see Valdichiana Toscana DOC) and to the south-west with the Orcia Valley or Val d’Orcia (see Orcia DOC). Within the nearby commune of Asciano there is a semi-arid and hilly area known as the Accona Desert.

Crete Senesi are literally the “clays of Siena”: the distinctive grey colouration of the soil gives the landscape an appearance often described as lunar. This characteristic clay, known as mattaione, represents the sediments of the Pliocene sea which covered the area between 2.5 and 4.5 million years ago. The landscape is characterized by barren and gently undulating hills, solitary oaks and cypresses, isolated farms at the top of the heights, stretches of wood and ponds of rainwater (commonly referred to as ‘fontoni’, literally “big springs”) in the valleys. Badlands and ‘biancane’ are typical conformations of the land. A notable edifice of this area is the Abbey of Monte Oliveto Maggiore, located 6.2 miles (10 km) south of Asciano. The region is known for its production of white truffles.

Bill Nesto & Frances Di Savino (2016, p.232) note that as there is no woodland, just tilled fields, the ‘crete’ is prone to erosion with landslides ocurring during periods of heavy rain, exacerbated by excessively heavy farming practices, like deep ploughing. The result, they say, is bare, pastel-tinted blue-grey embankments of clay called calanche or calanchi in the plural which did not feature in the artist Ambrogio Lorenzetti’s masterpiece, Buon Governo, commissioned in 1336 by Siena’s governing council.