This Sanctuary of the Bona Dea was excavated in the years 1938-1942. Only the lower part of the walls was found, because the building was razed to the ground in late antiquity. The goddess had another sanctuary in region V (V,X,2).
The Bona Dea or Good Goddess was a deity of fertility and health, both for people and the land. She is usually depicted as a seated matron, holding a snake and a horn of plenty. In Rome she had temples on the Aventine (rebuilt by Livia, the wife of Augustus) and in Trastevere. We know that in the former temple snakes were kept, and that the building contained a pharmacy. Only women worshipped the goddess. Sacerdotes or magistrae and ministrae were in charge of the cult. Secret rites took place in early December, led by the wife of a magistrate. A female swine was then sacrificed, and wine, music and dance played an important role in the festivities.
The oldest building phase (opus reticulatum and latericium) has been dated to the first half of the first century AD. The sanctuary (33.20 x 17.35) consisted of rooms C, D, E and F, with a little temple to the south-west of these rooms, and a courtyard with porticus to the east and south of the temple. The complex was surrounded by a high wall. A simple entrance, 1.70 wide, led to room C, in which a tufa altar was found (0.50 x 0.50). Corridor D leads to the courtyard. From here room F could be reached. On the floor of this room was a mosaic, preserved quite well along the west wall, perhaps because a wooden cupboard was standing here.
To the south of room E is a little temple (9.40 x 6.80). It was not built on a podium. The facade had four columns, of which only the travertine bases have been preserved. Between the columns are travertine thresholds, the central one 1.60 wide. In the pronaos are the remains of a black-and-white mosaic, depicting a large tabula ansata (a tablet with "handles") with a text, of which only a few letters have been preserved. The cella has a travertine threshold and a black-and-white mosaic on the floor. In front of the temple was a tufa altar (1.45 x 0.70). To the east and south of the temple was a courtyard, surrounded by a portico with brick columns (diameter 0.41).
Later rooms A and B were added (opus latericium). In the entrance of room A is a travertine threshold, with travertine columns on the ends, against the jambs. Room B has a black-and-white floor mosaic. In front of the room, outside the building, is a well. A basin (Ninfeo IV,VIII,4) was set against the north-west facade of the building.
In the last quarter of the third century major modifications took place. The entire south part was separated from the temple. Rooms G were now created (opus vittatum and latericium), that were perhaps used for commercial purposes. There was still a small courtyard to the east of the temple, but the porticus to the east of that was abandoned (a single brick pier has been preserved here). The back wall of the temple was rebuilt: the temple became smaller, the street to the west was widened. In room E a brick pier and some basins were built. As we have seen the building was eventually demolished.
Five large, marble dedicatory inscriptions are related to the temple. One was found inside the complex and can still be seen there. Fragments of the other four were reused elsewhere in the city. The five inscriptions are identical.
M(arcus) Maecilius M(arci) f(ilius) Furr[---] duovir
Aedem Bonae Deae ex sua pecunia fac(iundam) cur(avit)
M. Maecilius Furr..., mayor, built the Temple of the Good Goddess with his own money, and approved it. It is beyond me why so many dedicatory inscriptions were made.