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. Access is by foot -unless you own one of the villas on this stretch of road which were originally built illegally.
The dedication is to the Blessed Virgin Mary, under her title of "Mother of God".
The edifice was originally built as a domed tomb in the 4th century, but its history is lost. When new it had a pillared loggia surrounding it, but this was robbed long ago.
The monument was 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. However, it was abandoned itself later in the Middle Ages, and is now a well-preserved ruin. Owing to its shape it has the nickname "Priest's Birretta" (Berretta di Prete).
It is a brick cylinder with a low conical dome, on the left hand side of the road.