On the exterior side of the Walls, next to the western tower of Porta San Sebastiano, a portal with a travertine frame is clearly visible. The threshold, of which no trace remains, was located higher than the original Via Appia. The opening of the passage inside the Walls is almost completely hidden by the modern embankment.
Iconographic sources and stylistic studies allow us to date the construction and use of this portal, and the two analogous ones at Porta Ostiense and Porta Tiburtina, to between the late 15th and early 16th century. Their construction was probably related to the jubilees that brought a considerable influx of pilgrims to the city, for whom these “pedestrian passages” would have been created.
The opening was certainly walled up as early as the 16th century.
