Castello takes its name from a preexisting castle that risen on the northern high ground of the suburb. Today only remain a few rests of the "Castrum Zirri": the base of a tower and parts of the wall. According to the legend, the castle was possession of the marquises Malaspina. The last descendant was killed with one shot by the father of a girl of Osti family. As per the "ius primae noctis", the young maiden had to give herself to the Malaspina on her first married night.