The main organizing feature is a rectangular courtyard (A; 21 x 40 m.), surrounded by a portico with brick piers. In the corners of the east part of the courtyard are two large basins, triangular and curved, an unusual shape (55, 56). They may have been used during drills of the use of pumps and of bucket chains. In room 51 is an unusual threshold: two grooves suggest that a wheeled vehicle left the room, possibly carrying a pump (the distance between the centre of the grooves is 1.20). The courtyard was paved with bipedales, as were the three vestibules.

In room 2, to the north of the main entrance, a black-and-white geometric mosaic was found. On the walls of the room are paintings of panels, columns and a male figure. Unfortunately it is not obvious for what purpose and who used the room. Rooms at the west end may have been used by administrative personnel and officers (46-50). The fire-fighters themselves may have lived in some of the rooms around the portico, but certainly on the upper floors.

Plan of the barracks. Sablayrolles 1996, fig. 4.

The west side of the building was originally taken up by a row of shops, not connected with the barracks (19-27; Hadrianic or perhaps early-Antonine). In the Severan period these rooms were added to the barracks: the shop-entrances were blocked, and doors were opened leading to corridor B. At the south end of the corridor a basin was installed (57). In room 27 a cult niche was hacked out. These interventions have been linked to a few inscriptions from 207 AD, in which Septimius Severus and his son Caracalla are called restitutores castrorum Ostiensium, "restorers / rebuilders of the Ostian barracks". From other inscriptions has been deduced that the Emperors had doubled the number of vigiles in Rome, and presumably in Ostia and Portus as well. The total must then have grown from 320 to 640, divided between Ostia and Portus. It is not clear where the extra men lived. Through the interventions at the west end not much space was added. Rainbird suggests that part of the upper floors of the building was rented out at first, and that this space was occupied by the vigiles to accommodate the extra men. It seems unlikely however that ordinary citizens would be allowed to watch drills and other activities in the courtyard, from above. Perhaps a second, new building was erected, not yet excavated, or perhaps one of two buried and only partly known buildings to the east of the barracks was used.

Latrines

Two large latrines were found in the building. One, in room 18, has already been mentioned. The other was in the south-east corner of the building (42). It contains a small shrine dedicated to Fortuna. It is next to the door in the west wall, and may be called a hanging aedicula, that is, a mini-temple without a base. The excavators reconstructed it from marble fragments that had fallen on the floor. From bottom to top the aedicula consists of three consoles (starting at height 1.60 from the floor), a bottom slab, two tiny columns, a top slab, and a tympanum (the total height is 1.14). On the tympanum is the inscription:

The aedicula must have contained a statuette of Fortuna. Around 200 AD the Christian author Clement of Alexandria wrote: "The Romans, although they ascribe their greatest successes to Fortuna, and believe her to be the greatest deity, carry her statue to the privy, thus assigning to her a fit temple" (Protrepticus 4,45; translation G.W. Butterworth). It is a cynical comment that confirms, but does not explain, the presence of Fortuna in latrines.

A marble altar was found in front of the aedicula, with an inscription:

The Augusteum

At the west end of the courtyard, opposite the main entrance of the building, is an Augusteum, a large shrine dedicated to the cult of the Emperors. It consists of a rectangular "cella" (11.68 x 6.60), in front of which is a vestibule or "pronaos" (9.68 x 4.10) that was added in the Severan period. In the entrance of the pronaos are two marble columns. Between the pronaos and cella is a single step. Two brick piers may have replaced marble columns when the vestibule was added. On the floor of the pronaos is a large black-and-white mosaic depicting three phases of the sacrifice of a bull. To the left are a dead bull and a man with an axe. In the centre a man is leading a bull to an altar with a burning fire. To the left of the altar is a junior priest with a long axe (popa), to the right are two more men. One is playing a double flute, the other seems to hold a dish (patera) in his hand. The right part of the mosaic is very similar to the left part: we see a man with an axe (victimarius) and a bull.

Plan of the Augusteum. NSc 1889, page 78.

The foundation of a masonry altar was seen in the centre of the cella. On the floor is a geometric black-and-white mosaic, the lower part of the walls was decorated with marble. Against the back wall is a podium (w. 8.80, d. 1.57, h. 1.45) that was originally lined with marble. On top of the podium are five marble bases for small statues, perhaps made of (precious) metal. They are dedicated to Antoninus Pius, Marcus Aurelius, Lucius Verus and Septimius Severus. The dedication to Septimius Severus is on an erased text. Originally it may have been another dedication to Lucius Verus, who was presented as co-ruler of Marcus Aurelius. A base with a dedication to Lucius Aelius Verus Caesar, adoptive son of Hadrian, is standing against the right wall of the room.

In front of the pronaos are several other bases. Dedications to Septimius Severus, his sons Geta and Caracalla, and his wife Iulia Domna (all from 207 AD) were set against the columns and brick piers of the facade. The text for Geta was erased after he had been murdered in 211 AD by his brother. To the left are dedications to Caracalla, Gordianus III, and his wife Furia Sabinia Tranquillina. The whole series thus ends in 244 AD. In room 18 a base with a dedication to Diadumenianus (Emperor in 218 AD) was found.

Graffiti

Many graffiti were found in the building. These are discussed on a separate page in the topic "Fire-brigade".

Free grain

In room 44, to the south of the main entrance, a small, arched wall-niche was hacked out. It is surrounded by holes that may have supported an aedicula-facade. Also in the walls of this room are three shallow, rectangular recesses. These once contained small marble inscriptions that recorded the granting of the right to free grain to vigiles. After three years of service the vigiles were entitled to free grain supplied by the Emperor. A collection day and counter in the Porticus Minucia Frumentaria in Rome, where the grain of the frumentationes was distributed, were allotted. Similar texts were also painted on the walls, often in a tabula ansata (the inscriptions and painted texts can be found on separate pages in the topic "Fire-brigade")

The departure of the vigiles

The absence of dedications to Emperors after Gordianus III has been taken to imply that the vigiles had left Ostia in the second half of the third century, but this is just an argument from silence. The latest coins found in the Ostian barracks are from the years 355-363 AD. In a late phase some rooms with a small oven were created in the north-east part of the building (52-54). Below staircase 5 two late burials were found.