The Fortezza della Verruca is located in the municipality of Calci, on top of the Monte della Verruca, in the eastern Monti Pisani high ground. It dominates the entire Pisan plain and the flow of the Arno river. Its strategic position has always proven as effective support for the safety of Pisa, for centuries involved in warfare against Florentines: the stronghold afforded visual triangulation between Pisa and Vicopisano Castle, connected in turn with Buti Castle and the entire Pisan mountain chain.
Documented history of the settlements begins in 780. The fortress has always formed an almost impregnable stronghold for all armies and powers wanting to conquer the surrounding area: in 1288, during the war between the Pisan Guelphs and the Lucca army; in 1328, following the German invasion by Ludwig of Bavaria; in 1363, during the Florentine invasion; in 1369, following the invasion of Charles V of Bohemia’s troops and John Hawkwood’s English. In 1402, after Pisa was conquered by the Florentines, the stronghold was destroyed so that it wouldn’t become a threat. The Florentine troops won Verruca back again after long and bloody clashes on June 18 of the same year. It proved the final blow for Pisa’s hopes of independence and the city ended up in Florentine hands six years later. The fortress’s current appearance is the result of strengthening work after the countless wars.
La Verruca is regarded as an inconsistent building due to the various stages and architects who built it. Based on a pentagonal plan, it has two circular large towers at the front, thanks to sixteenth-century restoration work and two pointed bastions at the back. The front door, which preserves the trilithic structure, grants entrance into the fortress. Inside there are two construction levels: the higher one, which suffered the most damage, and the lower one, completely underground. The walls are one of the few examples of bastions built in stones in place of the typical terracotta bricks used at the time for this type of construction; cutting stones were only used for the corners and in a small quantity. The oldest part, dating to the eighth century, was built in local stone: the primary structure is functional, the inside of which contained barracks and arsenals, warehouses, a cistern and a church. The stronghold provides access to the side bastions, in which rooms were built from which to shoot or survey the surroundings. Numerous holes in the walls for firearms can still be seen today along the entire perimeter.
An important find was made in this stronghold: an epigraph, now in the San Matteo National Museum, which is almost certainly the first document to be written in Italian "volgare", on which one can clearly read "a dì dodici di giugno MCIII" (on 12 June MCIII).