Crete Senesi stretch in south-eas area of Siena. The name is derived from clay present in the soil, giving the landscape characteristic bluish-gray color and appearance often described as "lunar". This feature clay, mixed with rock salt and gypsum, is sediments from Pliocene sea that covered the area between 2.5 and 4.5 million years ago. The landscape is characterized by treeless and gently rolling hills, oak and cypress trees lonely, isolated farms on top of hills, stretches of forest in a hollow. Inside is a natural forest inhabited by squirrels and "nane" (mute ducks). The most interesting building in this area is St. Gimignano hostel, founded by initiative of St. Bernardo Tolomei, in the thirteenth century. The area is also known for the production of white truffle.