The House of Mars is on the intersection of the western stretch of the Decumanus and the Cardo degli Aurighi. It was excavated in 1938-9. The building was erected in the Hadrianic period (opus mixtum).
The south-east side, along the Decumanus, is taken up by three shops. Large piers were later set against the facade (supporting a branch of the aqueduct?). Two of these shops have doorways leading to the L-shaped vestibule of the building, that had its main entrance on the Cardo degli Aurighi. Two more shops could be entered from the Cardo. To the north of the vestibule is a courtyard (4.70 x 7.50). To the north-west of the courtyard is an accentuated room (4.70 x 4.70), to the north-east a long hall. The walls of the courtyard, the accentuated room and the hall were lined with marble, that has now disappeared (witness the mortar on the walls and holes in which the marble slabs were fastened). The floor of the accentuated room was decorated with marble, including reused inscriptions (suggesting a fairly late date). The building does not seem to have had any upper floors: no remains of a staircase were found, and the walls are rather thin (facade 0.50 - 0.52, inner walls 0.42 - 0.45).
Various modifications in opus vittatum can be seen, from the first half of the third century. The doorways between the hall and the courtyard were blocked, and a room was created at the north-west end of the hall. The passage between the vestibule and the courtyard was narrowed. The entrance from the street to one of the shops along the Cardo was blocked, and on the inside of the blocking three wall-niches were created: a semicircular niche, flanked by rectangular ones.
In the northern corner of the courtyard a marble altar with a dedication to Mars Augustus was found:
i.e. "Dedicated to Mars Augustus". Mars and the Imperial cult were merged. The plan of the building and the inscription suggest that this was the seat of a guild. One candidate is the guild of the public freedmen and slaves, corpus familiae publicae libertorum et servorum, because an inscription tells us that one of the members presented a statuette of Mars to the guild.
Plan of the building.
After SO I.