These buildings reflect the city's social stratification, from the densely packed multi-story apartments that housed laborers and merchants to the more expansive residences adorned with decorative mosaics, frescoes, and private courtyards. The architecture and layout of Ostia’s houses provide valuable insights into Roman urban planning, domestic life, and the adaptation of living spaces in a bustling port city.

As the principal harbor city of Rome, Ostia Antica developed a highly organized and functional approach to residential architecture. The majority of the population resided in insulae, multi-story apartment buildings that maximized limited urban space, often featuring shared courtyards, balconies, and access to communal water and sanitation facilities. Wealthier inhabitants lived in domus, single-family homes that demonstrated refined architectural styles and interior decoration, as seen in the House of the Paintings, the House of Bacchus and Ariadne, and the House of Jupiter and Ganymede. Some buildings, such as the Guild Seat of Trajan and the House, served both residential and professional functions, highlighting the economic interconnectivity of the city. The study of Ostia’s residential structures offers a detailed perspective on Roman domestic arrangements, social hierarchy, and the ways in which public and private life intertwined in an ancient urban environment.

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House of Serapis
The House of the Serapis (Caseggiato del Serapide), together with the Caseggiato degli Aurighi and the Terme dei Sette Sapienti constitutes one of the city's largest building complexes, unitary from a construction point of view. The building, of the Hadrianic era (circa 117-138 CE), had a courtyard with very tall brick pillars and at least two upper floors that could be reached from stairs located in the courtyard itself and occupied by apartments. In the early third century CE, a small cult building was constructed in the courtyard, with a stucco depiction of the god Derapis and other Egyptian deities at the sides. A gateway decorated with stucco reliefs was also built, with a frieze of bucrania (ox heads, originally holding religious significance), which gave access to the next-door Terme dei Sette Sapienti.

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House of Apuleius
The House of Apuleius (Domus di Apuleio) presents different phases of the construction, the first of which has been connected to thenearby small temples of the late republican period and may have belonged to the individual who built them, Publius Lucilius Gamala. The brick building now visible can be dated to aroundthe mid second century CE; the inscription preserved ona fistula (lead waterpipe) names the owner of the house during this phase as Lucius Apuleius Marcellus, perhapsto be identified as the author of the Metamorphoses, a famous literary work of the second century CE. The domus had a courtyard aligned with eight corinthian columns and an impluvium (central basin), with a row of rooms opening onto it to the east whilst other rooms were arranged in the west wing. Most of the rooms had mosaic floors.

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House of the Corridor
The House of the Entrance Corridor (Domus del Protiro), a luxurious aristocratic house, was built in successive phases during the third century CE. It was accessed througha monumental entrance (prothyrum) with marble columns and a pediment on which the owner's name was inscribed, erased in antiquity. It had a central courtyard, embellished with a nymphaeum decorated on both sides, with a curved front and niches facing the vestibule and a facade with aedicules and marble pediments facing the main room. The latter had two columns at the entrance and was paved with marble slabs; a similar veneer, partly made of reused materials, was present in the more luxurious rooms of the house. A small underground room with niches and a well could be reached from the courtyard and can perhaps be interpreted as a domestic sanctuary.

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House of Jupiter and Ganymede
The house (insula) of Jupiter and Ganymede (Domus di Giove e Ganimede), an apartment building, occupies part of the residential area known as the Caseggiato dei Dipinti of the Hadrianic period (circa 117-138 CE), with houses opening onto the street and a large communal courtyard at the rear. The layout has a central corridor and a small courtyard, serving to light the main room, located in the innermost sector of the house. The building takes its name from the subject of the mythological painting in the large reception room and was altered in the late second century CE, when the ceiling of this room was raised to a height of two storys and the painted decorations were made. At the same time the frescoes of the other rooms were also redonel they preserve a graffito dating to the period of the emperor Commodus (circa 180-192 CE). The mosaic floors belong to the building's original phase.

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House of the Well
The House (domus) of the Well or Cistern (Domus del Pozzo) was in the second half of the third century CE on the ground floor of an earlier apartment buillding (insula) of the Hadrianic period (circa 130 CE). Both the original entrance with brick half-columns andthe internal layout, arranged around a corridor with the other rooms opening onto it, remained almost unaltered. The main sector of the domus, to the north, consisted of an antechamber and a room whose entrance was monumentalized in the most recent phase with the insertion of two marble columns; in the same phase, new marble floors were laid in both rooms. An underground room, which can be interpreted as a cistern for rainwater or more probably as a storeroom for foodstuffs, could be reached from a staircase located in the main room.

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Remains of an Apartment Building
(Insula)

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House of the Dolia
The House of the Buried Dolia (Caseggiato dei Doli) complex hada commercial function and was built at the same time as the nearby Insula dei Dipinti during the Hadrianic period (circa 117-138 CE). It had a row of shops opening onto the street with a vast space behind them; in the early third century CE the latter was transformed into a storage area for large containers for liquids (oil and wine) that were is part set into the ground (dolia defossa). Some dolia still have numbers incised on them indicating their capacity in amphorae, a unit of measurement equivalent to about 26 liters. Inside the dolia about 400 terracotta moulds, perhaps for cakes, were found, with mythological, theatrical, erotic and circus scenes; thecakes may have been handed out during public banquets or sold during shows.

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House of the Paintings
The House of the Paintings (Casa dei Dipinti) is the modern name given to an apartment complex in Ancient Ostia. The house is a good example of the luxury living of a wealthy class of citizens in a large Roman city in the second century CE.

The House of the Paintings or Murals is the modern name given to an apartment complex in Ancient Ostia. The house along with a few other residential structures formed an insula with a magnificient central garden adorned with statues, benches and marble basins. This residential building once may have had either three or four storys. The luxurious apartment in the lower part consisted of twelve rooms; seven rooms were on the ground floor and five more on the first floor, with the reception rooms being about 6 meters high and the other rooms only 3 meters high. The house was built in Hadrianic times and remodeled in Severan times. However, it was probably still inhabited in the early Middle Ages. The murals (dipinti) that gave the house its name are now lost.

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House of the Lararium
The House of the Lararium (Caseggiato del Larario), shrine of the household god, was built in brick around 120 CE. The ground floor is largely taken up by shops. These could be entered from the street and from a courtyard. Vestibules are present in the south and west facade. The layout has been compared to the oriental bazaar.

The house is named after a polychrome niche, called lararium by the excavators, a shrine of the household gods, the Lares Familiares. However, in this niche must have been one, fairly large statue of a deity. The niche could not be placed exactly opposite the southern entrance to the building, but it is as close to the axis as possible. It functions as a religious welcome to those who entered the shopping centre.

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Insula of the Painted Ceiling
The Insula of the Painted Roof (Insula del Soffitto Dipinto), an apartment building, occupies the central part of a block from the Hadrianic era (circa 117-138 CE), used for both residential and commercial purposes. It developed on three or four storys, accessed from outside stairs. The house was reached from the street through a covered passage; it was arranged around a medianum (central vestibule) lit by tall windows, with the rooms opening onto it. Over time, the insula underwent transformations that involved the creation of small independent apartments. The painted decorations on the walls and one ceiling, still preserved in two rooms, may date to a renovation in the late second century CE; they reflect the refinedtaskte ofthe patrons of this period.

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House of the Fishes
The House of the Fishes (Domus dei Pesci), has two main building phases, that have been dated to the middle and the last quarter of the third century CE. The house is named after a white mosaic with a polychrome panel; a chalice with a fish, and two fishes next to the stem of the chalice. These may well have been Christian symbols, an interpretation that is not universally accepted, however. The panel was seen properly when people left the building, which suggests that it was a farewell greeting for Christians who had met in the house. In the courtyard a small statue was found of Fortuna with cornucopiae.

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Guild Seat of Trajan and the House
(Schola del Traiano)

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The Garden Houses
The Garden House (Le Case Giardino) built in around 130 CE as part of a vast construction project, had a mainly residential function though they also included commercial and servicespaces. The complex sonsisted of an external rectable and two central symmetrical residential blocks separated by an arealaidout as a garden with six fountains. The buildings, at least three storys high, and accessed from the garden, had external staircases leading up to the apartments located on the upper floors generally designed from rental. The complex as functional and elegantas a modern luxry class in an area near the sea and not too distant from the city center.

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House and Mithraeum of the Footprint
The Mithraeum of the Footprint (Caseggiato del Mitreo della Planta Pedis) was installed in a Hadrianic hall, between rows of piers of opus latericium and opus vittatum. The shrine had three naves. In the room to the east of the shrine are some basins and a well. In the west wall of this room is the main entrance of the shrine, on the east side of the central nave.

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House of the Nymphaeum
The house or domus of the nymphaeum (Domus del Ninfeo), a wealthy domus (residence), was constructed in the second half of the fourth century CE, in an area previously occupied by two building complexes of the early second century CE. It was entered through a courtyard which provided lightto the residence,embellished with a marble nymphaeum decorated with niches, opening onto the courtyard through a tripartite aperture was a huge room decorated on the floor and walls with opus sectile inlays, also preserved in other rooms of the domusa porticoed corridor leads to the inner most rooms of the house. The facade overlooking the Decumanus is enhanced by the presence of a large vestibule, divided into two rooms, originally decorated with wall paintings showing scenes of rural life.

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House of Bacchus and Ariadne
The House of Bacchus and Ariadne (Caseggiato di Bacco e Arianna) was built in the Hadrianic period (opus mixtum). The building was entered through a passage in the south part of the east facade. Here the road was spanned by four brick arches. Directly behind the entrance is a large courtyard with a basin in the centre. Originally a wide passage in the south-east corner led to the Temple of Serapis to the south. The building seems to have been related to the temple, like the House of the Serapeum further to the south. In the building the members of a religious guild related to Serapis (cultores) may have met and dined.

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House of Diana
The House (casa) of Diana (Caseggiato di Diana) complex, perhaps originally four storys tall with shops facing onto the street, was built in the Hadrianic period (first half of the second century CE). It has a central porticoed courtyard and over time underwent significant alterations to both the internal walls and the floors. The black and white geometrical mosaics in some rooms, the polychrome mosaic on one side of the portico and the inlaid marble floor of the triclinium belong to the original phase. In the second half of the second century CE, the courtyard was embellished with a fine marble nymphaeum whilst the surviving paintings were made at the end of this century. During the third century CE, the floors were raised and new mosaics were laid. Finally, a mithraeum was installed in the innermost rooms at a later period; it had a shrine, a (reused) marble altar and podia (benches made of masonry).

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House of the Thermopolium
The House of the Thermopolium (Caseggiato del Termopolio), used as an inn with a wine bar, was installed in the third century CE inside a complex of Hadrianic era (first half of the second century CE). It opened onto the street with threee entrances, provided with seats and covered by balconies resting on brackets. The interior was divided into three rooms; the middle one had a bar counter, shelves and basins for washing dishes made of marble. The still like paintings above the shelves show the foods served in the bar. One of the rooms, used as a kitched, had a dolium (large terracotta container) set into the ground for keeping food cool. The courtyard behind with a little fountain and masonry seating, allowed the patrons of the establishment to eat in the open.

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House of the Fortuna Annonaria
The aristocratic domus House of the Fortuna Annonaria (Domus della Fortuna Annonaria), whose current appearancedates to the fourth century CE, was installed inside a house of the mid-second century CE of which it preserved theperistyle in the central courtyard. The entrance was monumentalized with a prothyrum (colonnaded entrance) that led into a vestibule. This in turn gave access to the large courtyard, against the back wall of which is a cast of the statue of a goddess identified as Fortuna Annonaria (the goddess of food supplies) or as a personification of Ostia. The main room was adorned with marble, a fountain and probably statues; the apse must have hosted the stibadium, the semi-circular triclinium couch on which meals were eaten. A privated room of the house was converted into a heated room andpaved with a mosaic depicting mythological scenes.

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Seat of the Augustales
The Seat of the Augustales (Sede degli Augustali) is a building complex believed to the seat of some guild. The construction was first carried out in the ppus latericium style during the reign of Antoninus Pius of Marcus Aurelius. Known modificatons have been dated to the last three dacades of the third century CE, in the style of opus vittatum. The main entrance is through the northern facade, a marble porch leading to a vestibule, and a secondary entrance was through the eastern facade. The building is dominated by a large courtyard, surrounded by a porticus with brick piers. In the north-east corner is a transitional room, reached from the vestibule. The eastern part of the porticus is 6 meters wide, the other wings 3.50 meters. In the centre of the courtyard is a basin, originally revetted with marble, and with concave ends. In the south-west corner of the porticus is a well.

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House of the Wrestlers
The House of the Wrestlers (Caseggiato dei Lottatori), from the layout of the building, has been identified as a seat of a guild. The guild has been suggested that of the wrestlers. It has been dated to the Hadrianic period (opus latericium). The building is centered around a courtyard with a large basin. The courtyard is surrounded by a porticus. Of the six columns of the porticus (only four of which can be seen on the plan) only the travertine bases have been preserved. In the north part is the vestibule, between the two shops. A drinking fountain was set against the east wall, now disappeared.