Semicircular shaped, the fortified tower (also called Porta Rondella) was built at the beginning of the sixteenth century (between 1526 and 1529). It was supposed to replace a pre-existent gate, located in the eastern side of the city wall. Initially, the entrance of the village was a round arched portal, currently incorporated in the wall. But there, the original stoned arch can still be seen, and at its top there is the Latin inscription “FIRMI-PETROLIUM”, placed over two emblems.

Under the emblems, a date can be seen: 1529. It is not there to remind the foundation year of the defensive structure, but to remind when the Castle was given back to the rule of Fermo.
The fortified tower is topped by blind brackets, which, to sustain its terminal part, widen and then close, creating a sort of frame with chiaroscuro contrast.

Recent studies support the theory according to which the fortified tower was partially buried, losing its slope, which supported its massiveness. Due to the construction of the town hall, which was risen behind the eastern side of the tower in 1782, Porta Rondella has lost its roof and its interior furnishing.