The poor state of preservation of the Great Store Building is in sharp contrast with its importance. Many of the large tufa blocks from the outer west and east wall were reused in the Casone del Sale - the present museum -, perhaps built during the 15th century. Two lime-kilns were found in the building. The east facade was unearthed by Lanciani in 1885-1886, most of the building was excavated by Calza at the end of the First World War.
Click here for a colour-coded overall plan of the building (Bukowiecki - Rousse 2007, fig. 39).
Work on the Grandi Horrea was begun during the reign of Claudius. The building was accessed from the north, that is from the Tiber quays. At the north end was a porticus of tufa columns, resting on travertine bases. The west and east wall were made of large tufa blocks (h. 0.53-0.66, w. 0.59) with an intentionally rough surface (opus quadratum / opus rusticum). This building technique was chosen either to give the building an impressive appearance, or to safeguard it from fires. The back (south) wall was made of latericium. All inner rooms (cellae) were rebuilt later. They were arranged around a U-shaped courtyard, surrounded by tufa columns with doric, travertine capitals. The floors were made of opus signinum. The original building had no staircases and no upper floors.
During the reign of Nero or shortly afterwards long rows of rooms were added to the east and south. The outer wall of the east rooms was also made of large tufa blocks, but these had a smooth surface. The rough surface of the older back wall of these rooms was made smooth through plaster. The walls between the rooms were built in latericium. The rooms had a mezzanine floor. In the centre of the row is a staircase. In front of the row was a porticus of travertine columns.
The walls of the south row are in latericium. These rooms too had mezzanine floors, and the porticus in front of the east rooms continued in front of the south rooms. Between the south rooms are three staircases with travertine treads. The travertine thresholds of these rooms are rather enigmatic. It seems that, originally, they were smooth, suggesting that the rooms had no doors. At some point in time a depression for a door was hacked out in the centre. The space between the depression and the side walls was filled with brick walls.
During the reign of Marcus Aurelius and Commodus many rooms were rebuilt in latericium. Suspensurae (raised floors) were added, to protect the goods that were stored from vermin and moisture. At least one floor was added, witness four staircases, with travertine steps, in the corners of the interior.
The north part of the building was raised and rebuilt, with suspensurae, under Septimius Severus and in the later Severan period. From now on the building had only one, narrow entrance, in the centre of the north wall. The two northern staircases were replaced by staircases of eight treads followed by a sloping ramp, in order to facilitate the carrying of goods by porters. In the north-east part a cult niche was installed.
Supporting bricks piers and arches were set against the outer south wall. On Via dei Molini - the road to the west - five arches, spanning the road, were added. Between these arches two small rooms were set against the west wall of the building. In these rooms the lower part of two staircases was found: two treads and a landing, the latter to support a ladder. The ladders cannot have been used for transporting goods. 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 the rebuilding in the Severan period the building had only one, narrow exit.
Various other modifications cannot be dated accurately:
A group of coins found below a collapsed wall in the north part indicates, that the building was no longer in use at the end of the fourth century.
This very large depot has always attracted much attention. Citing Rickman: "Its size, complexity and solidity, and not least its position, all indicate that the Grandi Horrea was a publicly owned storehouse, and the presence of suspensurae, at least from the middle of the second century, would indicate that perishable foodstuff, probably grain, was stored in it." According to Hermansen the ground floor of the original building alone could hold 5.660 to 6.960 metric tons of grain. If we assume that one person needed five measures (modii) of grain per month, then the building would have contained grain for one year for 14.000 to 17.300 persons. After the addition of an extra floor the number must have been much larger (but if the building contained reserves for one year, the number must be halved).
First phase (Claudius).
Rickman 1971, fig. 11.
Second phase (Nero - Commodus).
Rickman 1971, fig. 12.
Final phase (Severan and later).
From Rickman 1971, fig. 10.