Even before the birth of St. Sebastian Cemetery, a necropolis was formed; the word "nekropolis" comes from the Greek, city of the dead.

three fine decorated mausoleums face here, the monumental facades are very similar, all masonry, consisting of a central door surmounted by an inscription with the owners' names.

The necropolis is distinguished by its perfectly preserved state. Its frescoes and stuccoes are a unique example of Roman funerary art between the 1st and 2nd centuries.

In the 3rd century they were buried to build a memorial site to the apostles Peter and Paul, discovered by chance in the year 1922 during the excavation of the memorial.