In 1561 the inhabitants of Castelnuovo
, that lay below in the valley and was so exposed to the attacks of Lucca, deemed necessary to reinforce the rocca
, anciently known as 'Monti', until then an administrative building and residence of the Duke of Este's officials. In 1578 Duke Alfonso IInd
, with the financial contribution of the villagers, entrusted the architect Marcantonio Pasi with the preparation of a project for the new walls.
The following year work was started according to Pasi's plan with twin bastions
like at Verrucole
. The walls were completed in 1584 and work then concentrated on the buildings within. In 1585 'Monti' was renamed 'Montalfonso' in honour of the Duke and equipped with the latest artillery. At the centre of the fort were a great cistern to collect rainwater, an underground casemate with a spiral staircase and the headquarters. Later, in 1617, a melting oven was added in order to reduce the considerable expenses of providing ammunition for heavy artillery.