This is one of the most famous monuments situated on the Via Appia. It consists of a cylinder covered with travertine slabs, having the upper part decorated with a marble frieze representing festoons and oxen's heads, all resting on an imposing square pedestal.
The presence of the reliefs of oxen's heads accounts for the name of "Capo di Bove" (Head of Ox) used to indicate the area in the Middle Ages. Above the entrance there is an inscription with the name of the owner of the tomb, Caecilia Metella, daughter of Quintus Metellus Creticus, the consul that conquered the Island of Crete in the year 67 B.C..
The mausoleum can be dated back to the end of the first century B.C., although it was probably used at least up to the second century A.D.. During the Middle Ages the large tomb became an important checkpoint on the Via Appia, so that in the eleventh century it was incorporated into the fortifications of a castle built by the Counts of Tuscolo.
In 1299 Pope Boniface the Eighth transformed the castle into a real fortified citadel surrounded by a battlemented wall with rectangular towers, including also a church dedicated to San Nicola. In the course of time the ancient mausoleum became the main tower of a fortified village that belonged to the most powerful Roman families.