The huge Warehouse of the Grain Measurers was built in the Trajanic period (opus mixtum, c. 112 AD). It has been related to the grain measurers, because their guild complex (I,XIX,1-3) invades the south-eastern part of the building. The building is aligned with the Tiber, not with the road (Via della Foce) to the south. The north end has not been excavated.
The building was entered from Via della Foce through two ornamental entrances with pilasters. It consists of rooms to the west and east of a long courtyard, flanked by arcades. To the west of the courtyard is a double row of rooms. Many of the rooms are huge, c. 12 metres wide, with piers supporting the ceiling. To the west of the Hall of the Grain Measurers is a wide ramp leading to the first floor (later a few steps were added).
To the west of the double row of rooms is a long corridor, continuing along the north and south side. It has a floor of opus spicatum. To the west of the corridor are wide rooms with restorations that have been dated to the late third or early fourth century (opus vittatum). Few commercial buildings near the Tiber were restored at such a late date.
The size of the rooms and the proximity of the guild seat of the measurers suggest that this was a grain measuring centre, rather than a warehouse. The measuring of grain will have taken place when cargo ships were unloaded and tow boats on the Tiber loaded. In Rome a guild of grain measurers using some sort of machines is documented (corpus mensorum machinariorum frumenti publici). Unfortunately we do not know what these machines looked like. They may well have been used in Ostia as well, in spacious areas, perhaps also in the neighbouring building I,XX,1.
