Mention Roman cities and most people think of a rigid grid. The orthogonal regularity of colonial cities stands as a metaphor for the comprehensive laws, military orderliness, and pragmatism of the Romans. Grid planning facilitated the establishment of new towns and districts, but was not universal. Many cities developed organically and settlements often abandoned right-angle layouts, expanding in response to topography, preexisting settlements, daily needs, and a preference for urban drama. Architectural historian William L. MacDonald drew our attention off the grid with his influential work on urban armatures. These major streets traversed cities, the entire length carefully choreographed with monuments, fountains, and colonnades to provide syncopated, sensorially rich experiences. Study of these impressive avenues has greatly informed our understanding of Roman design principles, but overshadowed consideration of less visually alluring urban features such as street traffic.

Roman cities were bustling places. In the mid second century CE they sheltered approximately 15 million people (5% of the entire world’s population). People flocked to Roman urban environments, drawn by the markets, politics, law courts, and innumerable urban amenities, from baths to spectacles. The Romans lived in the streets. Not only did they prefer the open air to overcrowded dwellings, but they derived status from being seen. Day and night people, parades, transports, and animals clogged urban thoroughfares creating noisy traffic jams. Large-scale construction projects and recurring public processions stalled urban circulation for days. In reaction, urban patrons commissioned buildings whose placement and design responded to, and directed, circulation. Arches mediated traffic speed and direction; steps restricted vehicle access to fora; walled temple precincts necessitated detours. Across the Empire, urban armatures provided the Romans with legible, attractive experiences freed from the tyranny of the grid while simultaneously, and no less subtly, addressing traffic demands.

In the course of the late-twelfth through fifteenth centuries, Siena underwent a radical physical transformation from a city of stone to a city of brick. The somber gray limestone towers and residences that for centuries had dominated its streets and squares gradually gave way to the warm red terracotta structures that today populate every corner of the municipality, to the point that celebrated historian Duccio Balestracci famously declared: “Siena è il mattone.”

It has long been understood that this material metamorphosis was conceived and executed by the Sienese Republic, which systematically introduced the brick industry into the city and, by the trecento, controlled every aspect of its production and distribution. Moreover, the ruling magistracies enacted legislation that not only established legal dimensions for every brick, but also mandated its use for palace facades and virtually all public works, including the Palazzo Pubblico, Mercanzia, ramparts, gates, fountains, and pavements. By the era of the Nine Governors (1287-1355), most major public edifices in the rural communities of the Sienese contado were also constructed of the same red medium.

Scholars have long assumed that the reasons for the change from stone to terracotta were purely practical, since excellent clay was locally abundant and bricks could be produced cheaper and more efficiently than ashlar, which had to be imported from great distances and at high cost. While these considerations may have been paramount until the early Duecento, starting in the Ghibelline era (1236-70) terracotta began to assume symbolic meanings that were increasingly promoted by the communal regime and eventually exceeded in importance the material’s utilitarian qualities. This paper will analyze and interpret the use of brick in early modern Siena and decipher the meanings, both political and social, that its government patrons intended to project.

The diverse afterlives of Rome’s ancient spectator buildings raise essential issues that intersect the fields of architectural history and urban development. While the theater of Marcellus was converted into a fortified compound, thus remaining a single building and retaining its monumental character, the stadium of Domitian became Piazza Navona, an urban space defined by numerous individual structures. The theater of Balbus lost its distinctive radial footprint, but kept a certain monumentality as it was reshaped into five Renaissance palaces. The amphitheater of Statilius Taurus, by contrast, was never found: it melted into the city and disappeared without a trace.

Seen together, these monuments offer an instructively varied series of core samples for an exploration of Rome’s evolution over time. Here, as in many long-inhabited cities across the Italian peninsula, the act of building almost always meant either displacing or repurposing earlier fabric. This was true not only as ancient monuments were reinhabited, but again and again as buildings were updated, repurposed and reshaped through the centuries. It seems only natural that historians of architecture would be interested in understanding this process of architectural/urban transformation as a whole. How did it affect the creative act? What happened to the urban environment when buildings migrated between types?

Surprisingly few conceptual tools are available for answering such questions. The most relevant text is Aldo Rossi’s The Architecture of the City, but while Rossi rightly understood the inextricable connection between buildings and the city, as a historian I have found his structuralist model of urban development ultimately unsatisfying. Rossi’s interpretation was much affected by his theoretical agenda as an architect practicing at a particular historical moment. This paper offers a critique of Rossi’s interpretive model, and explores some alternative avenues for understanding architectural transformations, and the city as an entity in perpetual flux.