The Hall of the Group of Mars and Venus was installed in the middle of the fourth century to the north of the Hadrianic shops II,IX,2 (opus latericium and vittatum). In the central north part a large apse was built, with a semicircular niche flanked by two rectangular ones. This was a nymphaeum. Several traces of the water supply were found, such as holes and water-pipes. Opposite is a small apse with a niche placed off-centre (later blocked). To the east is a room (6.25 x 6.25) at a somewhat higher level (0.70), accessed through a colonnaded entrance with four steps. In the north part of the west wall of this room is a floor-niche. The walls of the building were decorated with marble and plaster. Several rooms have floors of opus sectile.

Former shops along the Decumanus also belonged to the building. The one to the south of the raised room has a small wall-niche to the east of the door leading to the raised room (this niche was already present in the shop). A low marble bench ran along part of the walls of this room.

Traces of fire were found by the excavators, and the building does not seem to have been cleared after the fire. As a result many objects were found. Some important finds are:
- A large statuary group of Mars and Venus (h. of Mars 2.16; now in the Museo Nazionale, Rome). It was found on the floor, in many pieces. It does not belong to the building, because the intact statue was too large for the doors of the building. Originally it must have been placed in a niche: the group loses quality when it is viewed from the side or behind. It has been suggested that the heads are portraits of Marcus Aurelius and Faustina or Commodus and Crispina. Recently it has been suggested that the group comes from a tomb, and represents a private couple.
- A fragment of a relief depicting a nude person with outstretched hands, standing in an aedicula. This is a Christian relief, probably of Daniel, without the lions.
- A funerary altar with griffins on the sides and with a deep elliptical hole in the top. On the front is the inscription:

D(is) M(anibus) A(ulo) LIVIO AGATHANGELO SEVIR(o) AVG(ustali) QVINQ(uennali) HEREDES

The building has been identified as a Christian church and as a guild seat.