Wanted by Sichelgaida and Roberto il Guiscardo, the Cathedral of San Matteo was built very quickly from 1080, shortly after the Norman duke conquered Salerno, on the ruins of an ancient early Christian basilica. At the time, the Benedictine doctor and Benedictine poet Alfano I was bishop of Salerno.
The structure of the cathedral was largely taken from that of the nearby Abbey of Montecassino, as can be seen from the presence of the longitudinal plan divided into three naves. There were elements of architectural novelty of Carolingian influence, such as the triapsed transept. The crypt of the Cathedral, then as today, kept the relics of the evangelist Matthew, brought to the city, according to the tradition of Gisulf I around 1000 AD.
It is said that until around 1830, these exuded a transparent and odorless liquid that was called “manna of St. Matthew“, which was collected by the faithful outside the crypt. Miraculous powers were attributed to it.
In addition to the remains of the Evangelist, the relics of the Salerno martyrs are also kept in the cathedral: Fortunato, Caio, Ante and Felice, who suffered martyrdom at the time of the persecutions of Diocletian (303-310 AD).