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The insulae: The apartment buildings of the ancient Romans

The insulae of the Roman Empire are a fascinating reflection of Roman architectural innovation and urban planning.

The insulae: The apartment buildings of the ancient Romans
A poor woman, living on the upper floor of an insula, gazing at Rome from her window. Illustration: DALL-E

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The insulae of the Roman Empire are a fascinating reflection of Roman architectural innovation and urban planning. These ancient apartment blocks, were designed to accommodate the dense population of one of history's most influential cities.

The insulae of Ancient Rome are a fascinating reflection of Roman architectural innovation and urban planning. These ancient apartment blocks, designed to accommodate the dense population of one of history's most influential cities, offer a glimpse into the daily lives of Roman citizens.

What were the insulae?

The insulae were the primary form of housing for the vast majority of Rome's urban population, which was estimated to be between 800,000 and 1 million people during the early imperial era. These apartment buildings were home to the common folk, including the lower and middle classes, (the plebeians) and even the more affluent members of the upper-middle class, (the equites) with the exception of the societal elite. Unlike the segregated housing of modern cities, the insulae and the domus—a type of spacious single-family home occupied by the elite—were interspersed throughout Roman urban areas.

The insulae were multifunctional structures, with the ground floor typically reserved for commercial establishments like shops, while the upper floors served as residential spaces. It was common for an insula to carry the name of its owner, who was often a member of the Roman elite, such as senators. Ownership of these buildings could also be shared among several individuals, as was the case with Cicero, who owned a portion of an insula and collected a corresponding fraction of its income. Residents of the insulae would pay rent for their living spaces, similar to the arrangement in modern apartment buildings.

The Foundation of Roman Urbanism

The term "insula" translates to "island" in Latin, aptly describing how these buildings rose like islands from the Roman cityscape. Initially appearing as early as the second century B.C.E., insulae were a response to the increasing need for housing within the bustling heart of Rome and its mercantile hubs like Ostia. Not only did they serve as residences for the city's burgeoning population, but they also housed shops and businesses on the ground floors, blending commercial and living spaces in a single structure.

An insula dating from the early 2nd century AD in the Roman port town of Ostia Antica.
An insula dating from the early 2nd century AD in the Roman port town of Ostia Antica. Credits: iessi, CC BY 2.0

Architectural Design and Structure

Constructed primarily from concrete (opus caementicium), the Roman insulae were early examples of high-rise apartment living, a concept that would not reappear until the Industrial Revolution. These structures could reach up to 10 or more stories, though the upper floors were less desirable due to safety concerns and were therefore cheaper to rent. The design of insulae varied from simple two to four-room apartments for the lower classes to luxurious accommodations for the wealthier citizens, featuring large glazed windows, gardens, courtyards, and sometimes even amenities like kitchens and piped water.

Livy, recounting the events of 191 B.C.E., noted an unusual incident where two domesticated oxen ascended a multi-story building, eventually reaching its tiled rooftop (Livy 36.37). This anecdote highlights the architectural evolution of Rome as early as the second century B.C.E., showcasing the city's early experiments with multi-level constructions. Strabo, during the Augustan era, pointed out the rapid urban development and the subsequent need for regulatory measures concerning building heights (Strabo 5.3.7). Vitruvius, meanwhile, offered a more optimistic perspective on the insulae, crediting advancements in building technology for the possibility of such complex structures (De architectura 2.8.17). In contrast, writers like Seneca and Diodorus Siculus expressed concerns over the insulae's crowded and unsanitary conditions.

The term "insula" itself is subject to scholarly debate regarding its exact definition and implications for Rome's urban landscape and population density. The Regionary Catalog, a document from the fourth century C.E., lists 44,850 insulae and 1,781 domus within Rome as of 315 C.E. (Regionary Catalog).

Glenn Storey (professor at the university of Iowa) interpreted these figures to suggest a total of over 45,000 standalone buildings in Rome at that time. James Packer (professor of classics at the Northwestern University) contributed to the discussion by suggesting that "insula" could refer to either a singular high-rise building or a segment of a larger edifice, emphasizing the complexity of Roman urban planning and the diverse interpretations of architectural terminology.

In addition to Rome, the insulae found in Ostia Antica offer valuable insights into the architecture of these apartment complexes during the 2nd and 3rd centuries AD, showcasing instances of more opulent insulae. The scarcity of surviving examples makes it difficult to gauge the prevalence of such upscale dwellings.

These luxury insulae typically featured a central rectangular space known as a medianum, serving as the hub for access to other areas within the apartment. The layout included varying-sized reception rooms, sometimes divided into two spaces or left as a singular large room, and were often illuminated by sizable glazed windows overlooking gardens, courtyards, or streets.

The presence of cubicula, generally two, was common alongside amenities like kitchens, latrines, and piped water on the upper floors, indicating a level of affluence. Decorative elements such as ornate pilasters or columns around the exterior doorways further suggest these insulae catered to the wealthier populace on a more permanent basis.

Conversely, Ostia also contained simpler insulae with two to four rooms catering to the lower-class residents. An example is the Casa Di Diana, where the ground floor featured a narrow corridor leading to dimly lit cells and presumably a communal living area. Such designs, also observed at Rome's Capitoline Hill, hint at a widespread architectural response to the high demand for housing.

Shared facilities like latrines and cisterns for drinking water were common among these less affluent quarters, often serving not only long-term residents but also providing temporary lodging for transient workers. Despite the lack of concrete evidence on the specifics of sharing these spaces, it's speculated that such arrangements were a necessity for the lower classes in ancient Roman society.

Living in an Insula: Pros and Cons

Living in an insula came with its unique set of advantages and challenges. On the one hand, these apartment blocks provided housing close to the city center, allowing easy access to public amenities, work, and markets. On the other hand, they were prone to fires and structural collapses, posing significant risks to inhabitants. To mitigate these dangers, Roman emperors such as Augustus and Nero imposed height restrictions and encouraged safer building practices.

The portrait of Augustus, the first Emperor of Rome. Illustration: DALL-E

Regulatory Measures and Safety Concerns

The dangers of fire and structural failure prompted regulatory reforms aimed at improving the safety of insulae. Augustus, for instance, restricted the height of insulae to 70 Roman feet, a limit that was further reduced by subsequent emperors in response to catastrophic events like the Great Fire of Rome. These regulations reflect the Roman government's attempts to balance urban density with safety concerns.

Strabo mentions that, similar to domus, insulae were equipped with water supply and sewage systems. However, these residential buildings were often hastily constructed with the aim of maximizing profits, leading to substandard quality. Constructed from materials like timber, brick, and eventually Roman concrete, these structures were vulnerable to fires and structural failures, a point highlighted by the satirist Juvenal.

Marcus Licinius Crassus, known for his ventures in real estate, owned several insulae in Rome. Cicero is famously quoted as expressing relief when one of Crassus's poorly constructed buildings collapsed, as it presented an opportunity to levy higher rents on a newly constructed replacement. The layout within insulae typically featured the smallest living spaces on the highest floors, while the more spacious and costly apartments were situated on the ground level. Because of safety issues and extra flights of stairs, the uppermost floors of insulae were the least desirable, and thus the cheapest to rent. 

Gismondi's scale model of the Capitoline Hill under Constantine, Museum of Roman Civilization. Credits: Jean-Pierre Dalbéra, CC BY 2.0

The Capitoline Insula: A Case Study

The Capitoline Insula, dating back to the 2nd century CE and located on Rome's prestigious Capitoline Hill, serves as a well-preserved example of Roman insulae. This particular insula, built using a combination of brick and concrete, featured five floors with diminishing ceiling heights, indicating a socioeconomic gradient among its inhabitants. The Capitoline Insula's unique construction and the social dynamics it housed provide valuable insights into the complex nature of Roman urban living.

The Roman insulae were more than just ancient apartment blocks; they were a testament to the architectural ingenuity and urban planning of Ancient Rome. By accommodating a wide range of social classes within the constraints of their society and technology, the insulae reflect the complexities and challenges of life in the Roman Empire. For modern historians and archaeologists, these structures offer a window into the past, revealing the daily lives, social structures, and architectural achievements of one of history's greatest civilizations.

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