The Mausoleum with its base
The Mausoleum was built at the end of the 1st century BC, more precisely between 25 and 10 BC, and has a quadrangular concrete base eight meters high. You can still see the blocks of travertine that could not be removed in late antiquity, and all around the walls of the medieval Castle of the Caetani that incorporated it.
On a quadrangular base stands a large cylindrical building, with a diameter of 30 meters, which still retains the original cladding in travertine slabs and was crowned at the top by a battlement. The roof was domed, perhaps surrounded by a mound.
The cylinder was thirty-nine meters high and under the battlements you can still see part of a frieze with bucrania and garlands, typical of funerary monuments, from which the medieval name of this place derives: Capo di Bove.
The burial chamber is excavated inside the Mausoleum and has its same height; it was a hollow cylinder covered with brick curtain and covered by a dome of which only a circle with travertine blocks remains. It is accessed by a corridor (dromos) in the lower part of the Mausoleum.
At the end of the 13th century, due to its tower shape and its strategic location along the Via Appia, the Mausoleum became the centerpiece of the Castellum Caetani, the medieval fortifications that controlled access to the city of Rome. After the Caetani of Pope Boniface VIII, who also built the nearby church of San Nicola, it passed into the possession of various Roman families: the Savelli, the Colonna, the Orsini and finally the Torlonia.
The Torlonia family owned the nearby lands, where another large monumental tomb on the Appian Way stands: the Mausoleum of Romulus, the son of Maxentius who died in 309 AD, next to which the Circus of Maxentius was built where funeral games were celebrated in his honor.
The Mausoleum of Caecilia Metella was built in the same years in which Augustus built his own Mausoleum, the first large imperial dynastic tomb that we described in other blogs. They were certainly inspired by the large Etruscan mounds and also by the large monumental tombs of the Hellenistic era, such as the Mausoleum of Halicarnassus, one of the Seven Wonders of the World.
The funerary inscription of Caecilia Metella
Both served as a model for the Mausoleum of Hadrian, whose historical story is similar to that of the Mausoleum of Caecilia Metella: because of its circular tower-like shape it was transformed into a fortress and enclosed in the medieval fortifications of Rome to defend the access to the city, charging transit tolls.
All this is explained in detail in Marina De Franceschini's book «Castel Sant'Angelo. Mausoleum of Hadrian. Architecture & Light» which reconstructs its history and transformation from imperial tomb to impregnable fortress.