The main defensive structure of Ascoli is located on the eastern peak of the Pelasgian Hill, which dominates the plain below. The Annunziata Hill has been an important place for the defense of the area since pre-Roman times. The current fortress was built on the remains and according to the design of the ancient Cassero, built by the Piceni. The hill still bears the symbolic name of Monte Cassero. Over the centuries, the fortress has been rebuilt several times. It was destroyed and rebuilt by the conquerors and continued to dominate the city until the fall of the Roman Empire. In 1349, it was restored by Galeotto Malatesta, who, together with the Malatesta fortress, made it one of the cornerstones of the rule over the city. The fortress acquired its current appearance thanks to Pope Pius IV, who ordered its renovation in 1560. Renovation work was carried out over the following five or six years. The building was seriously neglected and was used as a quarry for the extraction of building materials. In 1857 it was bought by the municipality of Ascoli and donated to the Agricultural School, until it was moved to the new headquarters in the 19th century.