Mill-bakery I,XIII,4 was excavated between 1938 and 1942. A few remains can be dated to c. 80-100 AD. The main building period (opus mixtum) can be dated to c. 100-125 AD. The building was now a mill-bakery. Various modifications took place in the later second and in the third century (opus latericium and vittatum). The latest modifications (opus vittatum), in the north-west part, have been dated to c. 370-440 AD. The width of the inner walls (0.44-0.46) indicates that the building was not very high.
Along the Cardo Maximus, to the west, are four shops (rooms 1-2, 3, 5, and 6-7). Four more shops are along the Semita dei Cippi, to the east (rooms 12, 13, 15, and 16). The workshop could be entered from corridors 4 and 14, and from a narrow alley to the north (17-18-19). Wagons may have entered the building through corridor 14. At some point in time a staircase (D) was added here. Corridor 4 could be blocked by a beam that was inserted in L-shaped holes.
In the centre of the building is a large hall, with floors of basalt blocks. Only the northern part (8a) seems to have had a roof, carried by two long rows of brick piers. In the north part of 8a are five kneading-machines, made of volcanic stone. In the south part are eight mills of volcanic stone, surronded by mortar-beds. On three mills are inscriptions, perhaps the initials of the makers: S P C Y R, P A R, and M I V. Letters can also be read on one of the kneading machines: G I A H. The grain may have been poured into the mills from an attic, that was reached via staircase B.
The southern part of the hall (8b) did not have a roof. Here, in the south-east part, two cisterns were found, below the floor level. In the wall behind the cisterns the lower part of a curved wall-niche can be seen, which once contained a statuette of a deity. Two staircases (A and C) were set against the south wall.
The southern part of the workshop consists of rooms 9, 10 and 11. Grain and firewood may have been stored on the attic over these rooms. In room 9 was a large oven (inside diam. c. 4.50). Three layers of large tufa blocks have been preserved. They do not rest on a podium (unless the podium is still to be found below the present floor level). Four piers in the corners of the room carried arches and a concrete ceiling, necessary in view of the risk of fire and to contain the heat. In room 10 are the remains of another kneading machine. It is made of travertine. But this room was probably primarily used for the shaping of the dough into loaves of bread, over tables.
There must have been a stable for the animals who operated the machines, but its position is not clear. The bread was probably sold in the building, in the shops.
In area 8 a large number of bronze objects was found, that do not seem to belong to the building: simple vessels, lamps, two candelabra, a table support with a female herm (with some silver) and a bacchic mask that decorated the rim of a large vessel (situla) (Floriani Squarciapino 1949; the museum guide seems to suggest building I,XIII,2). Photographs are available in the Virtual Museum.