Roman domestic architecture – insula

House of Diane, Ostia Antica, (CC BY 2.0)

Insula of Diana, Ostia Antica, (CC BY 2.0) (source)

In the Latin language, insula (plural insulae) means “island” and the term has been connected to the high-rise apartment dwellings of the Roman world, presumably since they rose like islands from the built landscape of the city. The insulae of ancient Roman cities provided housing for the bulk of the urban populace. The plebs—defined as ordinary people of lower- or middle-class status—tended to inhabit insulae. During the heyday of the mercantile city of Ostia at the mouth of the Tiber river (less than 20 miles from Rome), a building boom produced many such insulae, making Ostia a city of high-rise apartments, a phenomenon of urban building that would not manifest itself again until the Industrial Revolution.

Reconstruction, House of Diane (CC BY-SA 3.0) (source)

Reconstruction, Insula of Diane (CC BY-SA 3.0) (source)


In relating the history of the year 191 B.C.E., the historian Livy remarks that two tame oxen had climbed the stairs of a multi-story building, ending up on the tiled roof (Livy 36.37). While this may seem a passing comment, it reminds us that even in the second century B.C.E Rome was a vertical city in the sense that buildings with multiple levels were already being built. Strabo (5.3.7), commenting on Rome in the time of Augustus, mentions the building boom there and the need to regulate construction, including the height of buildings. The architectural writer Vitruvius (De architectura 2.8.17) expresses a fairly optimistic view of the insulae, observing that advances in construction technology that facilitated the construction of these outstanding dwellings. Other ancient authors, including Seneca and Diodorus, were less positive about insulae, seeing them as noisy and squalid.

There is some debate among scholars about how, precisely, we should understand and define the term insula. A fourth century C.E. source, known as the Regionary Catalog, states that in the city of Rome there were 44,850 insulae and 1781 domus in 315 C.E. Glenn Storey observes that if these figures represent individual buildings, fourth century C.E. Rome had over 45,000 independent structures.  Understanding the meaning of the term insula, then, has obvious implications for understanding the population and organization of the ancient city of Rome. Scholars have debated how we should interpret the term. James Packer posits that insula connotes a high-rise building that could occupy an entire block or be a portion of a larger structure.

Insula dei Dipinti (Ostia) reconstruction (I. Gismondi)

Insula dei Dipinti (Ostia) reconstruction (I. Gismondi)

In this reconstruction, the larger building must have been subdivided into smaller units. These are the medianum and cenaculum, terms for subdivisions of the apartment building. Their specific meaning remains somewhat troublesome, but surviving records do indicate that apartment buildings were subdivided for legal reasons, as well as for assessing rent. James Packer estimates the median area of a Roman apartment at 239 square meters.


The apartment block differs significantly from the townhouse (domus). The domus is essentially a dwelling for a single, extended family unit, while the apartment block contains multiple units. The top-to-bottom arrangement of the Roman apartment block was the inverse of what is true in the twenty-first century: in the Roman world the best apartments were located at ground level, while the lower quality (and more squalid) units were to be found on the upper floors of the structure. There is a good deal of variation in terms of the organization of the structures themselves. Frequently the entire structure centers on an open courtyard which also serves as a light well for the lower floors. The spaces fronting on the street itself were often used for mercantile functions.

Reconstruction drawing of block III , X by Italo Gismondi. From the north-west. From left to right: House of Serapis, Baths of the Seven Sages, House of the Charioteers

Reconstruction drawing by Italo Gismondi. From left to right: Caseggiato del Serapide (House of Serapides), Terme dei Sette Sapienti (Baths of the Seven Sages), Cas. degli Aurighi (House of the Charioteers) (source)

The port city of Ostia provides the best evidence for the Roman apartment block. Ostia had been founded as a Roman colony during the third century B.C.E. Its location at the mouth of the Tiber river was important for both mercantile and strategic reasons. During the second century C.E. its economy and population was booming, as was the population of the city of Rome. As a result the city witnesses an intense spate of building activity, including the construction of numerous insulae.

The  Caseggiato del Serapide shows an example of a block with shops at the ground level, while staircases lead to apartments on upper floors. The courtyard contained a cult room with a stuccoed relief of the god Serapis.

The so-called Garden Houses (Case a Giardino) provide an example of second and third century C.E. luxury apartments that were later converted to commercial use. This structure originally stood to four floors (height of c. 17.70 metres or 60 Roman feet according to Stevens) and had 16 units on the ground floor. The central architectural feature is the garden courtyard at the center of the structure to which the apartments communicated.

Ostia: Plan of Regio III - Insula IX - Case a Giardino (Garden Houses)

Ostia: Plan of Regio III – Insula IX – Case a Giardino (Garden Houses) (source)

The original walk-ups

The apartment block demonstrates the pragmatism and innovation of Roman architects who capitalized on their technical proficiency with concrete (opus caementicium). Cities like Rome and Ostia are unusual in the ancient world—their large and concentrated populations required solutions like the apartment block. These structures, despite Vitruvian enthusiasm, were not without their dangers and drawbacks. Since fire was a frequent danger in the ancient city, the high-rise apartment was particularly risky—especially for those dwelling on upper floors. The living conditions in some cases may have been less than ideal as well. The insula as an architectural type demonstrates the variety of Roman architecture and provides another set of important data about Roman domestic building.



Additional resources:

Ostia: Harbour City of Ancient Rome

Roman Housing on the Metropolitan Museum of Art’s Heilbrunn Timeline of Art History

Guido Calza, Scavi di Ostia, 1: Topografia Generale (Rome: Libreria dello Stato, 1953).

Rina Cervi, “Evoluzione architettonica delle cosidette Case a Giardino ad Ostia” in L. Quilici and S. Quilici-Gigli (eds.), Città e monumenti nell’Italia antica, (Atlante tematico di topografia antica 7), (Rome: “L”Erma” di Bretschneider, 1988) pp. 141-156.

Filippo Coarelli, Rome and environs: an archaeological guide, trans. J. J. Clauss and D. P. Harmon (Berkeley: University of California Press, 2007).

Alfred Frazer, “Modes of European Courtyard Design before the Medieval Cloister,” Gesta, vol. 12, no. 1/2 (1973), pp. 1-12.

Bruce W. Frier, Landlords and Tenants in Imperial Rome (Princeton, N.J. : Princeton University Press, 1980).

Bruce W. Frier, “The Rental Market in Early Imperial Rome,” The Journal of Roman Studies, Vol. 67 (1977), pp. 27-37.

G. Hermansen, “The Medianum and the Roman Apartment,” Phoenix, vol. 24, no. 4 (Winter, 1970), pp. 342-347.

Russell Meiggs, Roman Ostia, 2nd ed. (Oxford: Clarendon Press, 1973).

James E. Packer, “Housing and Population in Imperial Ostia and Rome,” The Journal of Roman Studies, vol. 57, no. 1/2 (1967), pp. 80-95.

James E. Packer, The Insulae of Imperial Ostia (Memoirs of the American Academy in Rome, vol. 31) (Rome: The American Academy in Rome, 1971).

Carlo Pavolini, Ostia (Bari: Laterza, 2006).

John Stambaugh, The Ancient Roman City (Baltimore: Johns Hopkins University Press, 1988).

Saskia Stevens, “Reconstructing the Garden Houses at Ostia. Exploring Water Supply and Building Height,” BABesch 80 (2005), pp. 113-123.

Glenn R. Storey, “Regionaries-Type Insulae 2: Architectural/Residential Units at Rome,” American Journal of Archaeology, vol. 106, no. 3 (Jul., 2002), pp. 411-434.

Glenn R. Storey, “The Meaning of “Insula” in Roman Residential Terminology,” Memoirs of the American Academy in Rome, vol. 49 (2004), pp. 47-84.

Carol Martin Watts and Donald J. Watts, “Geometrical Ordering of the Garden Houses at Ostia,” Journal of the Society of Architectural Historians, vol. 46, no. 3 (Sep., 1987), pp. 265-276.


Cite this page as: Dr. Jeffrey A. Becker, "Roman domestic architecture – insula," in Smarthistory, February 27, 2016, accessed September 29, 2016,