Santa Maria Genitrice a Via Appia is a ruined church on the Via Appia Antica, just beyond the eighth milestone which is about as far from the city as the Ciampino airport nearby. This is in the Castel di Leva zone.
The edifice was originally built as a domed mausoleum in the late 3rd or early 4th century, but its history is lost.
When new it had a pillared and barrel-vaulted loggia surrounding it, and was connected to the street frontage by a covered corridor widening out into two apses presumably for statues. These features were robbed long ago, but foundations survive of the corridor. Next to it are traces of rooms the original function of which is unknown.
The monument was apparently converted into a church in the 10th century, a surprising fate given that most of the suburban churches of Rome were being abandoned in the Dark Ages. The surviving reference dates from the year 954.
The structures in between the church and the street might then have functioned as a monastery.
However the site was abandoned very soon after, and the church was apparently used as a pigeon-house. It was converted into a little fort in the 12th century, by the addition of an upper storey which has now left few traces in the fabric.
By the end of the Middle Ages, the building was being used as a farmhouse by lower-class people (terroni). This is deduced from the rubbish and poor-quality pottery left in the floor to be found by archaeologists.
It is now a well-preserved ruin. Owing to its shape it has the nickname "Priest's Birretta" (Berretta di Prete).
It should be noted that the identification of the mausoleum with the church depends on the coincidence of localities -the eighth milestone. A query has been raised about this -it might be that the church was actually nearby.
The edifice is a double cylinder, the upper one with a smaller diameter and the join between the two having a gradual slope. The upper cylinder is topped by a low conical saucer dome, of concrete and with a central oculus or circular opening.
The fabric is in brick, but including courses in cubes of flint which is a building technique dating to the end of the 3rd century.
The single entrance is a very tall round-headed portal, reaching the entire height of the lower cylinder. Four round-headed niches occur in the wall of this. Similar niches adorn the interior.
The building is on the east side of the ancient road, just north of the crossing of the Via di Fiorenello.
Access is by foot -unless you own one of the villas on this stretch of road which were originally built illegally. The plot of land on which the edifice stands is railed off, so you cannot approach very closely.