The building materials of San Martino Fortress in San Piero a Sieve (Tuscany, Italy)

The Medici Fortress of San Martino dominates the village of San Piero a Sieve and a large part of Mugello intermountain basin. Its construction was promoted by Cosimo I de 'Medici in 1569 as a bulwark in defence of the possessions of the family and of the Florentine state and to meet the demands of local populations, to have protection against the continuous pillages perpetrated by armies and bands from the north. It has a polygonal perimeter, including embankments and seven bulwarks. Inside there is a chapel and a donjon with houses for the troops of the Grand Duke of Tuscany. The project is by Baldassarre Lanci and its construction was then completed by Simone Genga and Bernardo Buontalenti. The complex was equipped with effective systems to resist sieges, such as cisterns, warehouses for food and weapons, casemates, kitchens, windmills, armouries, workshops for the repair and construction of cannons and other firearms. Moreover the hill on which the fortress stands was crossed by a secret passage that led to the Sieve river, in order to bring the horses to watering. After the earthquake of 1762 the fortress was closed by the Grand Duke Leopold I of Tuscany who considered it useless, and the peasants of the area went there to inhabit. Later it was abandoned. Almost reduced to ruin and forgotten, today it is undergoing restoration. The study will examine the natural and artificial stone materials used for the building according to mineralogical and petrographic methodologies and will verify any variations that occurred during the construction phases.