The Fortezza Medicea of Volterra is built on the highest point of the hill overlooking the town.
Despite its name, the origins of the fortress predate the ascendancy of the Medicis. The southern part was constructed at the command of the Walter VI, Duke of Athens who had been appointed governor of Florence in 1342.
For more than a century the once friendly relationship between Volterra and Florence became increasingly complicated and at times confrontational: the discovery locally of valuable Alum in the 1470s focused the interest of Florence, and in 1472 7,000 Florentine troops besieged and then sacked the town, after which Florentine control over Volterra and the alum mines was no longer in doubt.
Wikipedia https://en.wikipedia.org/wiki/Fortezza_Medicea_(Volterra)
Address 51 Via di Castello, Volterra 56048, Italy
Coordinates 43°23'59.99" N 10°51'53.672" E