Castle stands on top of Bonadies Mount over-looking the city of Salerno. It named Arechi because the construction of this fortification is associated, traditionally, with Lombard Duke Arechi II. A rectangular plant, the tower was built on five or six levels, with the control function of the harbor below. Normans did not make changes, but realized an extension to the south by a portico of which there are some piers. They were responsible for the construction of the tower called "La Bastille", on a rocky outcrop north of Castle. Ceramic and glass finds are numerous and of high quality, demonstrating that Castle also had residential function. The last renovations date back to Angevin period 1299. With Aragonese Castle reached the peak of development were built large buildings visible east of the so-called Plaza de Armas. Majolica Neapolitan, Florentine and Vietri sul Mare attest that stayed lords. In 1992 Italian Post Office have dedicated a postage stamp. In Castle Museum displays artifacts from the excavations carried out on the site.