The castle of Serravalle is called Rocca Nuova because there previously was a fortification that does not exist today and that is recalled by the "Torre del Barbarossa" on the Eastern side of the town. The Rocca Nuova dates to the XIV century and it exists thanks to the short presence of the population of Lucca in Serravalle.

The Rocca Nuova was founded after the year 1302, when the inhabitants of Lucca conquered Serravalle. The date of foundation of this structure is uncertain, while without any doubt Uguccione della Faggiola was given supervised the works, initially. Castruccio Castracani later finished them and he settled the construction of the tower and chose the Rocca as his residence and headquarters for his militia.
Later on, Florence bought the castle in 1351 and Cosimo I chose it as the seat of a town hall. Once, the two fortresses enclosed the whole village inside their huge walls, but today it is only the restored and open to the public Rocca Nuova that overlooks Serravalle. The hexagonal tower and the storage tank of the castle are very well preserved. There are also big parts of walls and a turret oriented to Northeast. The part of the bastion adjacent to this turret highlights the possibility for the militia that garrisoned the stronghold to cross its walls and perform their patrol.
The door of the Gabella opens on one part of the XIV-century walls. This door is one of the junction points between the old and the new fence. By crossing it over, one can arrive to the village of Gabella Vecchia, the ancient best-preserved built-up area in the town as many readable inscriptions on its stone houses recall. This door added to the pre-existent ones of Castellina and Nievore built in the XII century.