Along the Via Appia the most important families of Roman antiquity built their tombs, to have great visibility andahow everyone their wealth and importance. One of the most impressive tombs is the Mausoleum of Cecilia Metella.

In 310 AD. also the emperor Maxentius chose the prestigious Via Appia to build the tomb of his son Romolo Valerio, who died prematurely at the age of only fifteen. The land had long belonged to the Imperial House and included the ancient villa of Herodes Atticus, the so-called Triopio.

Near the Mausoleum, the emperor built a large Circus, where funerary games were held in honor of his son. At that time, the Roman calendar had sixty-five days dedicated to various Ludi Circenses (Circus Games), which the emperor watched from a oryal box reserved for him, known as the Pulvinar Imperiale, which still exists.

The Mausoleum of Romulus is located inside a large squared enclosure which was a "temenos", i.e. a sacred space. The perimeter walls are more than ten meters high, and inside there was a monumental portico with pillars, covered by cross vaults that have collapsed.

The shape of the Mausoleum recalls that of the Pantheon, because it had a rectangular building with a pronaos with columns which preceded the actual Mausoleum, circular in shape. The pronaos disappeared and the building was transformed into a farmhouse by the Torlonias, from which one enters the sepulchral crypt, which has remained practically intact.

It is a circular construction with a diameter of 33 m, which on the outside must have been covered with blocks of travertine like the Mausoleum of Cecilia Metella.
Inside it has a large central pillar supporting a ring barrel vault, which covers the corridor that runs all the way around.

In the pillar there are eight alternating rectangular and semicircular niches, which correspond on the perimeter wall as many niches with "wolf's mouth" windows from which the sun's rays enter. The imperial sarcophagi were placed in the niches.

The main entrance to the Mausoleum at the pronaos faced the Appian Way and is astronomically oriented, so that the Sun enters it at sunset on the Winter Solstice (as discovered by Prof. Roberto Brunelli).

The illumination had a precise symbolic and religious meaning, linked to Sol Invictus, which in late antiquity became a State cult, replacing the Saturnalia in the Winter Solstice rituals.
Sol Invictus was identified with Romulus, who was deified after his death. Being divine he legitimized the imperial succession of Maxentius, even if his reign lasted only a few years.