Emperor Otto I of Saxony, having conquered Italy, was proclaimed Emperor of the Holy Roman Empire in Rome in the year 962. To consolidate imperial power and control the territory he has a series of fortresses built. Precisely these seem to be the true origins of the Greenhouse Grange.
In this ancient fortress, from whose towers one overlooks the city of Siena and its territory, from Mount Amiata to the Crete to the Chianti hills, Frederick Barbarossa and Frederick II are said to have passed through. The latter would have appointed as his vassals the Cacciaconti, a powerful family that would later control much of the castles located south of Siena and would have expressed saints, such as the Blessed Bonizzella, and brigands, such as Ghino di Tacco.
At the end of the 1200s the German Empire lost its influence in Italy and the fortress was ceded to theOspedale di Santa Maria della Scala in Siena, which turned it into one of its most powerful Grance, fortified farms needed to support the flow of pilgrims from northern Europe along the Via Francigena to Rome and Palestine, embarking from the ports of Puglia.
The Grancia delle Serre is first mentioned in a document from 1210, but its growth was marked by generous donations of land and real estate from noble families, including the Piccolomini and Cacciaconti families. Among the most significant legacies was that of 1297, when Bernardino di Alamanno Piccolomini donated 23 plots of cultivated land, 12 houses and olive groves within the castle to the Hospital of Santa Maria della Scala in Siena. This impressive heritage formed the basis for the development of the complex.
Initially, the Grancia consisted of two towers located on the walls of Serre Castle, next to St. Lawrence Gate. Over the years, these facilities were expanded and integrated into a more comprehensive system. In the 14th century, agricultural needs and the threat of raids led to the construction of new buildings and the fortification of the complex with walls, towers and patrol paths.