During the first half of the 4th century, anonymous authors compiled a pair of very similar catalogs of Roman buildings and landmarks, the Notitia and the Curiosum urbis Romae regionum XIIII, the “Description” (Notitia) and “Gazetteer (Curiosum) of the fourteen regions of the city of Rome.” Updated at least as late as the year 357, they listed noteworthy features of each of the city’s fourteen regions, the administrative subdivisions, like Paris’s arrondissements or London’s boroughs, that had been introduced by Augustus in 7 BC (Fig. 1.1). The two Regionary Catalogs, as they are now called, are the most comprehensive resource we have for the names and places constitutive of Rome’s urban fabric at the end of antiquity. For some areas, they are graphically supplemented by the surviving fragments of the Severan Marble Plan, a gigantic 1:240 scale map of Rome carved circa AD 203 into marble slabs mounted on a wall in the Forum of Peace (Fig. 1.2).

We begin with the cataclysms, both local and systemic, that set Rome on a wholly new course. Between about 410, when Alaric’s Goths became the first non-Roman army to capture and pillage Rome in 800 years, and the middle of the 6th century, when Byzantine and Gothic armies pulled the city apart in a murderous tug-of-war lasting almost two decades, the urban population declined by a full order of magnitude, from over a half-million to something like 50,000. A millennium would pass before the latter figure was again exceeded. Even at the height of Italy’s communal age in the 13th century, when the mercantile and banking centers of Milan and Florence boasted 100,000 residents or more, Rome had maybe 50,000, a number equaled or exceeded also by Venice, Genoa, Bologna, Pisa, Siena, and Palermo.

The relative textual and archaeological invisibility of the 10th and 11th centuries at Rome is especially vexing for coming at a critical transitional period, just when the early medieval city began to metamorphose into the very different sort of place it became in the later Middle Ages. The later medieval city as it emerged from the 12th century on broke with its ancient roots in a number of ways. At least as late as the 9th century, upper-class residences like the ones in the Forum of Nerva retained a distinctly unfortified profile; though these houses were smaller and more compact than the aristocratic mansions of imperial Rome, they nonetheless prolonged a tradition of accessible, ‘civilian’ residential architecture that had continued unbroken for a thousand years. By the 12th century, however, Roman nobles lived in fortified compounds, complete with defensible outer walls and tall towers. As late as the 10th and 11th centuries, very few churches had bell towers, either; the soaring, graceful campanili attached to surviving medieval churches only proliferated in the 12th. In the 9th and 10th centuries, patches of settlement still extended across much of the intramural area.

Rome in the century and a half after the Byzantine reconquest is characterized both by deep structural continuities with the past and by often profound ruptures and innovations that pointed toward the future. In purely topographical terms, however, the past prevailed. Some old monuments and infrastructure were retained in something close to their original condition, others were altered and/or repurposed, and many more were left to decay for want of sufficient human and material resources. In all cases, though, the physical contours of the ‘Byzantine’ present mostly consisted of features first created centuries earlier. Streets and piazzas, walls and aqueducts, housing and churches inherited from the imperial era still defined the parameters of the material environment in which Romans lived and worked.

Over the course of the 8th century, Rome finally became what papal apologists (medieval and modern) claimed it had been centuries earlier: an effectively autonomous polity ruled by popes and administered by bureaucrats and functionaries employed by the Church. After a lengthy gestation period stretching back into the 7th century, this papal “Republic of the Romans” (respublica Romanorum) matured in the second half of the 8th, under Frankish protection, and flourished into the later 9th. It comprised the city itself and a surrounding territory, roughly coextensive with the modern region of Lazio, that fell under direct Roman jurisdiction. During the century and more of the papal Republic’s apogee, the popes claimed, and flaunted, privileges and prerogatives previously reserved to Romano-Byzantine emperors, becoming in the process the first sovereign rulers to reside stably in Rome since the 5th-century emperors. Only at this point does it finally become proper to speak of a ‘papal’ Rome where the Church, led by the popes, was the dominant force in shaping the cityscape (Fig. 4.1).

As Frederick I (“Barbarossa”) approached Rome for the first time in 1155, on his way to be crowned Emperor of the Romans by Pope Hadrian IV, he was met by Roman envoys at Sutri, a day’s journey north of the city. Nothing in the young German king’s prior experience, even among the recalcitrant city communes of northern Italy, had prepared him for the blithe insolence of his visitors, who proclaimed themselves representatives of something called the Roman Senate. From the parchments they read aloud upon entering Frederick’s presence, the majestically condescending voice of Rome personified rang out. Lady Roma spoke to the king as a mistress to a suppliant come to beg from her and the Senate the favor of an imperial coronation. The city, via the Senate that – this particular personified Rome suggested – embodied her will and incarnated her ancient glories, would deign to grant Frederick the imperial crown provided he obediently satisfy a long list of conditions, all punctually enumerated.

The period covered in this chapter, from the death of Pope John VIII in 882 until the beginnings of the papal reform movement in the mid 11th century, has traditionally been treated as the blackest of the early medieval ‘Dark Ages’ at Rome. The perspective is understandable, and not entirely wrong. The written sources decline markedly in quality and quantity from the second half of the 9th century, while the few 10th-century narratives that survive tend to present the Roman scene in bleak terms. Historians of art and architecture have had still less to go on. Not a single monumental edifice survives from the years 882–1046. As far as we know, in fact, not a single really monumental edifice was built for two centuries after the fortified circuit erected circa 880 by John VIII around the peri-urban nucleus at St. Paul’s

There is substantial consensus that the years around 1230 represent a sociopolitical inflection point at Rome, when the “barons” began definitively to surpass the rest of the urban nobility and constitute themselves as a class apart – the barones Urbis as opposed to the ordinary nobiles Urbis. This local superelite, never exceeding 12–15 families, would exercise “a crushing hegemony over Roman political life” for more than a century, until the popular backlash that crystallized around Cola di Rienzo in 1347. Even then, their eclipse was temporary. Across the period c. 1230–1420, the barons were the most consistently influential actors on the Roman stage. Whether as cardinals (and sometimes popes), senators, or ‘private’ agents, they would play an outsized role in shaping – for better and for worse – the urban environment for the rest of the Middle Ages: for better, in that baronial patrons sponsored a preponderance of the most impressive monuments and artistic commissions attempted in Rome; for worse, in that they subverted the mechanisms of communal government and made Rome the arena for their bloody rivalries.

In december 1450, as the festive and very successful Jubilee year was drawing to a close, tragedy famously struck at Ponte Sant’Angelo. It was evening, and thousands of pilgrims were coming back from the Borgo to their lodgings across the river. As the flow of pedestrians on the congested roadway over the bridge slowed and stopped, those behind continued to push ahead; in the resulting squeeze, the parapets of the bridge gave way and some 200 people died, either crushed above or drowned in the waters below. Pope Nicholas V Parentucelli reacted decisively in the wake of the disaster. He expropriated the shops and stalls that packed the approaches to the bridge on the Campus Martius side (using some of the piles of cash collected during the Jubilee to compensate the proprietors), and leveled them to create an open esplanade hundreds of meters long and dozens of meters wide, with the road running through the center. Around the periphery of this sort of grand boulevard, the Canale di Ponte, rose regular rows of new shops for the bankers and merchants who crowded into this strategic crossing-point between the Borgo and the city-center.