Click here to open a plan of the building in a new window (Bakker 1999, figs. 12a-b).
The excavation of the House of the Millstones was completed in the years 1913-1916, by Raffaele Finelli and Guido Calza. The building had been excavated partially in 1870 by Carlo Ludovico and Pietro Ercole Visconti. Because of political events the Visconti's could not finish the excavation. Ostia was property of the pope, but on September 20th 1870 king Victor Emanuel captured Rome. The pope retreated to the Vatican, and Ostia was from now on under the authority of the new Italian state. After the first excavations the building was named Casa di Aquilina, after a stamp on a lead water-pipe, found below the pavement of Via dei Molini. When the excavations were continued in 1913, most of the rooms that had previously been excavated had been filled with earth again. Objects found in the building were stolen twice: in 1870 and 1959.
Phase 1: the Hadrianic period
The building was erected in the early second century AD, during the reign of Hadrian (opus mixtum). It consisted of shops along Via dei Molini, a hall at the intersection of Via dei Molini and Via di Diana (1-3), and two halls (17-18, 19-21) and a few rooms behind the shops. In the east facade two recesses for reliefs have been preserved. One is now empty, in the other is a terracotta relief of a Genius with cornucopiae and patera, and a snake. The snake represents the Genius Loci, the protective deity of the place.
Phase 2: the Antonine period
In the Antonine period the House of Diana was built to the west. There was an alley between the two buildings. In the same period the House of the Millstones was modified (opus latericium). Shops 15 and 16 were built or perhaps rebuilt. Slender brick piers were set against the west and east wall in halls 17-18 and 19-21. They do not seem to have supported a roof. Room 17 seems to have been the only part of the halls that was covered, witness beamholes. Room 8 apparently had a special status. It was not accessible from the street, but received light from it through two windows. Two more recesses for (lost) reliefs were added, in the east and south facade. There are two external staircases: room 4 (already a staircase in the Hadrianic period) and room 9. The steps rested on wooden beams, fastened in small holes in the lateral walls. The first floor in the east part of the building was at a height of a little over four metres. Via di Diana was partly blocked by a short wall set against the east end of the facade. There is a pendant across the street.
Phase 3: the Severan period
Important structural modifications took place in the Severan period (opus latericium). Five sub-phases have been recognized. The modifications began during the reign of Septimius Severus (193-211 AD). The work was finished during the first decades of the third century. The main alteration was the raising of the level of the upper floors. A new first floor was installed at a height of c. 6 metres. The other upper floors must also have been rebuilt. This destabilized the building and counter-measures had to be taken.
The new first floor was supported by arches in rooms 6, 7, 17 and 19-21. The two arches in hall 19-21 are huge. A pier in the centre of hall 17-18 must have carried beams. Staircase 9 was rebuilt. Behind the staircase a small room (11) was created. The alley was closed off at the north end by room 29, which has a barrel vault. Five piers were set against the east facade, and another five opposite these, across the street, against the Grandi Horrea. The piers obviously supported east-west running arches, and stabilized the building.
Phase 4: later third century and undated alterations
Some further alterations have been dated to the later third century (opus latericium and vittatum), other alterations could not be dated. Basins were installed in rooms 26 and 28. Room 27 is spanned by two high arches, that cannot be dated, even though one of the piers is Antonine. The piers further stabilized the building. Another basin was built in room 21. Seven very large windows were hacked out, high up in the west walls of rooms 17-22. The remains of two large ovens were found in rooms 23 and 14. The one in room 14 was given up at an unknown date, and room 14 became an independent shop. In the west wall of room 23 are two holes, low in the wall, apparently draught-holes. In the north wall is the lower part of a niche or, more likely, chimney. Bar-counters were installed in shops 15 and 16. In the east side of the Severan pier between rooms 4 and 6 a relief was inserted with carpenters' tools: a saw, a plummet, two pairs of compasses, and rulers can be recognized. Water was piped into the building through a lead pipe, from the workshop of Iulia Aquilina, below Via dei Molini and entering the building in room 7. All walls in the building were at one time plastered (a total of seven layers has been recognized). On the east facade the excavators saw traces of red letters on a thin, white background. Between two of the piers on the east side of Via dei Molini two tiny rooms were built, both with a low podium with a few treads, that once supported a ladder.
Drawing of the relief with carpenters' tools. NSc 1913, p. 206.
The find of millstones, kneading-machines and floors of basalt blocks show that the building had become a bakery. The workshop will be discussed in more detail below.
Reconstruction drawing of the building in the Severan period (Jan Theo Bakker).
Seen from the south-east.
The fire and the finds
The building was destroyed by a fire. The excavators saw traces on walls and floors, and found a thick destruction-layer (1.5 to 3 metres high). The fire can be dated fairly accurately. No masonry in the building can be dated to the time of Diocletian or later. Many coins were found. The series ends under Probus (276-282 AD). Apparently the building was destroyed in the last quarter of the third century, perhaps as the result of an earthquake, of which several traces have been found in Ostia. After the fire at least the lower part of the ruins was left undisturbed. On Via dei Molini parts of the walls of the building were found, and on top of these a thick layer of rammed earth: a path had been created at an average height of 2.20 above the Hadrianic street level.
Numerous objects were found in the building, such as keys, locks, revetment of furniture, lamps, candelabra, strigiles, and kitchen utensils. In bar 15 a complete amphora and parts of amphorae were found. Parts of horse-harnesses, a ring for tying up animals to a wall, and bells must be related to the bakery (the bells rang when the hopper was empty). Finelli reports the find of many lance-heads, but these were in fact dosage-cones, that were inserted in the lower part of the millstone (meta). Grain flow-control was achieved by suspending a hopper over the conical end of the cones. Many tools were found: hammers, hatchets, chisels, axes etc. These must have belonged to the carpenters, whose presence in the building is attested by a relief. Presumably they had specialized in the maintenance of the millstones and their wooden frames. The distance between the lower and upper part of the millstones was of great importance: if it was too big, the grain would fall through; if it was too small, the grain was burned.
A number of objects had fallen down from one or more surprisingly wealthy apartments on the upper floors: parts of bronze revetment of furniture were found (sometimes with silver inlay), elaborate candelabra, fragments of marble and terracotta friezes with amorino's, parts of black-and-white mosaic floors with geometrical patterns and floral motifs, fragments of painted ceilings, parts of opus sectile, and tesserae of glass-paste.
In the south-west part of the building a shrine was found, the Sacello del Silvano (room 25), that is described on a separate page. But from the finds can be deduced that there was at least one more shrine in the building. In 1870 thirteen statuettes and one small bust of deities were found. During the same excavations a gold ring was found with an aureus of the Emperor Decius (249-251 AD), perhaps related to the cult of the Emperors, and lamps (some from the workshop of Annius Serapiodorus) with depictions of the Pastor Bonus. The precise place of discovery of the 1870-finds is not known. In room 14 part of a vessel with the depiction of a bat (the mammal) was found. The bat may have had an apotropaic purpose. In room 15 a small snake, possibly the Genius Loci, and an approximately 0.60 high marble statue of the armed Venus came to light. Perhaps in room 16 a statuette of Mercurius was found. Eight statuettes were encountered in rooms 17-19. One of these, a scorpion, is perhaps to be related to the cult of Mithras. A tiny octagonal column with base and capital, found in the same rooms, may have formed part of an aedicula. Also from these rooms come seven rectangular bronze sheets, with depictions of signs of the Zodiac and the symbol of a planet (average height 3.8 cm.). They were attached to something by means of nails. According to Floriani Squarciapino they are to be related to magical practices or the cult of Mithras (note that in the mithraeum in the adjacent House of Diana a Petronius Felix Marsus is documented, a snake-charmer, who was thought to have occult powers). In the same rooms a gorgon-mask, part of the handle of a vessel, was found.
It seems unlikely that the building housed a bakery in the second century, in view of the absence of a large, roofed area for milling. It was installed in the Severan period, when room 29, with a barrel vault, was built. The only barrel vaults in the building are in this room and the adjacent oven-room 23. Barrel vaults slow down the cooling of an oven and do not catch fire as easily as a ceiling resting on wooden beams.
It is probably not a coincidence that opposite the Caseggiato dei Molini, across Via dei Molini, is one of Ostia's largest store buildings for grain, the Grandi Horrea, dating back to the reign of Claudius. There is however no exit related to the Molini in the west wall of these horrea. The ladders in the two rooms on Via dei Molini cannot have been used for supplying grain. Ladders are not suited for porters carrying loads. Because there are two ladders, many people were expected to use them. Possibly this was a fire escape: after a rebuilding in the Severan period the Grandi Horrea had only one, narrow exit. Presumably the grain was supplied over Via dei Molini, using a floor resting on the arches spanning the road, and on the two tiny rooms, that have surprisingly thick walls. The grain was then fed to the millstones through pipes. This hypothesis is supported by the find in the Molini of parts of masonry covered by opus signinum, which according to Calza had fallen down from the upper floors and possibly belonged to basins.
As to the interior of the mill-bakery, at least the rooms with a basalt floor and a high ceiling were used for the various steps in the bread making: 6, 7, 17 to 22, and 26 to 28. Millstones, kneading-machines and ovens bear witness to these activities. Basalt blocks with imprints of hooves are found in rooms 18, 19, and especially 7. They may indicate that the animals who turned the millstones had horseshoes. The imprints do not form circles, so that apparently blocks were moved, which is understandable, because the ruts created by the animals rotating the millstones will eventually have made them stumble, necessitating the replacement of worn blocks by smooth ones.
At least rooms 19-21 were used for the milling. This large hall has a floor of basalt blocks and a basin. Many millstones were found here (there must have been at least ten). The metae have a square hole in the top, with lead against the sides and on the bottom. On one catillus is the inscription CHRY. Inscriptions have also been found on millstones from Pompeii, Palestrina and Rome, and in the Ostian Molino I,XIII,4. They are initials or the beginnings of names, whose is not known. The volcanic stone the millstones are made of comes from Orvieto.
Five kneading-machines were found in room 22. Blades were inserted in holes in the sides. The grafting of the vertical spindle can still be seen in the bottom of the north-western one (iron and lead with a small, round hole in the centre). The basin in room 28 must have supplied the large quantities of water necessary for the kneading. Sieving took place during and after the grinding and before the kneading, possibly in room 21. The moulding of the bread was the first step after the kneading, and for this room 13 may have been used, where a wooden table may have rested on thin walls.
The remains of two ovens are reported. One was in room 23, the other in the east part of 23 and west part of 14. The oven in room 14 was abandoned after c. 250 AD. Rooms 29 and 23 had barrel-vaults, related to the oven in room 23, which was approached from the west. The missing of large stretches of masonry on the north and south walls of room 23 is probably also related to the oven. In the south wall the stretch is funnel-shaped and possibly the start of a chimney. In the dividing wall of rooms 29 and 23 are two draught-holes.
The oven in room 23 was uncovered once more in 1996. The floor in front of the oven is considerably below that of the other rooms. The oven is made of a cupola of tufa stones on top of a brick podium. In the front of the podium is a deep niche. Most interesting are four horizontal grooves inside the oven, in the tufa blocks: two wide ones, and two narrow ones above. Possibly they testify to the presence of one or more revolving grates on which the bread was baked, an understandable device, because the oven has a depth of almost five metres.
The long basin in room 26 looks like a trough, suggesting that a stable was nearby, for which room 17 is the best candidate. The threshold leading to room 26 from room 18 is very heavily damaged, probably the result of the passage of animals. Perhaps the bakers also used the Caseggiato di Diana as a stable. In the room to the south of its courtyard a trough and a basalt floor were installed, and there are also basalt blocks in a room to the east of the courtyard.
Rooms 17-22 were lit by large windows, that were probably also installed for ventilation. The various basins, also on the first floor, must have been served by Ostia's aqueduct. Lead water-pipes were found below the pavement of Via dei Molini, branching off to room 7, and below rooms 24 and 25. An important, if not the main entrance was room 12, along staircase 9 and the tiny room 11. On the south wall of room 11 is a fragment of a stucco relief, a more expensive kind of decoration, indicating that the room was of special importance: an office, or, as the excavators have suggested, a shrine.