The City Above and Below: An Introduction to Paris's Dual Landscape

The City Above and Below: An Introduction to Paris's Dual Landscape

When one descends the worn stone steps of a Parisian Métro station, passing through the turnstiles into the amber-lit belly of the earth, a transformation occurs that transcends the mere physical act of going underground. The vertical journey mirrors a conceptual passage from one city to another—from the Paris of grand boulevards, animated terraces, and Haussmannian facades to an entirely different metropolis, one that operates beneath the pavement with its own logic, its own history, and its own profound relationship to the visible city above. This book proposes that understanding Paris requires understanding both of these cities simultaneously, and that the relationship between them is not incidental but essential to comprehending what Paris is, how it came to be, and why it continues to evolve in the ways that distinguish it from any other capital in the world.

The image of Paris as a layered city—multiple urban surfaces stacked vertically, each with its distinct character yet utterly dependent upon the others—has long attracted writers, engineers, urban planners, and curious travelers. Victor Hugo, in his novels set in Paris, repeatedly drew attention to the sewers as the secret intestines of civilization, the hidden truth beneath the polished surface of bourgeois society. Jean Valjean, escaping through the Parisian sewers in Les Misérables, traversed not merely a drainage channel but the negative space of the city itself, the shadow that defines the light. Georges-Eugène Haussmann, while reorganizing the surface of Paris in the mid-nineteenth century, simultaneously transformed its subterranean anatomy, creating the sewer network that remains in use today as a marvel of engineering foresight. The underground, in other words, has never been simply functional; it has always been epistemological, offering Parisians and observers alike a way of knowing the city that surface observation alone cannot provide.

The Scale of the Invisible City

To appreciate the true magnitude of Paris's underground domain, one must move beyond the romantic imagery of the Catacombs with their neatly arranged skulls and the popular imagination of sewerdwelling rats. The physical infrastructure beneath Parisian streets constitutes an urban system of extraordinary complexity and scale, one that rivals the visible city in its comprehensiveness and surpasses it in certain dimensions of engineering ambition.

The Paris Métro, opened in 1900 for the Exposition Universelle, now encompasses over 214 kilometers of lines and 308 stations, making it one of the densest underground transit networks in the world. ${ }^{1}$ By comparison, London's Underground—older, larger in total length, and serving a metropolitan area of greater population—nevertheless operates with fewer stations within the historic city limits. The Métro's stations, many designed in the art nouveau aesthetic of Hector Guimard, create an underground cityscape of considerable architectural variety, from the ornate cerulean tiles of the Concorde station to the modern clarity of newer extensions. Each day, approximately 3.4 million passengers descend into this subsurface transit network, ${ }^{2}$ transforming what might be considered merely a transportation utility into a genuine underground commons, a shared space where all of Parisian society encounters itself in miniature.

Yet the Métro represents only one dimension of what lies below. The sewer system of Paris extends over 2,400 kilometers—longer than the distance from Paris to Istanbul by air—and processes an average of 2.4 million cubic meters of wastewater daily. ${ }^{3}$ This network, developed incrementally from the medieval drainage channels that preceded it, was fundamentally reimagined during Haussmann's administrative tenure under Napoleon III, when the engineer Eugène Belgrand designed the modern system that remains the backbone of Parisian sanitation. The sewers are not merely conduits for waste; they serve as routes for telecommunications cables, electrical conduits, and—increasingly—the fiber optic infrastructure that connects the twenty-first-century city. Walking the sewers, as maintenance crews still do in certain sections, is to traverse a cross-section of urban infrastructure, layers of utility accumulated over more than a century and a half of continuous development.

Beneath the sewers, often beneath the foundations of buildings themselves, lies the third major component of Paris's underground: the former limestone quarries that extend beneath approximately one-third of the city's surface area. These extraction galleries, some dating to Roman times and earlier, were largely exhausted of their limestone by the eighteenth century, leaving behind a vast subterranean void. ${ }^{4}$ The extraction network covers nearly 170 hectares and includes galleries reaching depths of 30 to 40 meters below street level. ${ }^{5}$ When these old quarries began collapsing in the late eighteenth century, threatening buildings above, the city was forced to create an entirely new administrative apparatus—the Inspection Générale des Carrières—to map, consolidate, and secure the underground voids. The quarries represent a geological history inscribed beneath the urban present, a reminder that Paris built itself from its own subterranean resources before it learned to build upon them.

Finally, there are the Catacombs, those famous ossuaries that contain the skeletal remains of approximately six million Parisians, transferred from overflowing cemetery graves during the late eighteenth and early nineteenth centuries. ${ }^{6}$ The Catacombs occupy approximately 1.7 kilometers of tunnels within the quarry network, their precise location—marked simply by "Arrête! C'est ici l'empire de la Mort"—creating a threshold between the living city and this immense repository of the dead. The Catacombs represent a unique phenomenon in urban history: the organized relocation of a city's dead to its geological depths, creating an underground landscape of macabre beauty that continues to attract visitors from around the world.

When these four major systems—transit, sanitation, quarry voids, and ossuary—are considered together, along with the electrical, telecommunications, and natural gas infrastructure that has been layered into and between them, the total volume of human-occupied or human-engineered space beneath Paris becomes staggering. Estimates suggest that the underground contains between 8 and 10 million cubic meters of voids that are either accessible to maintenance workers or potentially accessible in emergency situations. ${ }^{7}$ This constitutes an urban volume comparable to, or perhaps exceeding, the built space of many entire European cities.

Historical Layers: The Genesis of Paris's Underground

The relationship between Parisian surface and subterranean did not emerge full-formed; it accumulated over centuries, with each era adding its own layer to the urban palimpsest. Understanding this historical development is essential to understanding why Paris's dual landscape took the particular form it did, and why it continues to influence the city's development in ways that are simultaneously practical and symbolic.

The earliest subterranean activity in what would become Paris was, of course, the extraction of building materials. The soft limestone known as "pierre de Paris" or "calcaire lutétien"—formed from marine sediments deposited approximately 45 million years ago—was quarried from Roman times onward. ${ }^{8}$ The Romans, who established Lutetia on the left bank of the Seine, built extensively with this limestone, and evidence suggests they began extracting it from underground galleries rather than open quarries as early as the first century CE. ${ }^{9}$ The gallery method of extraction, which left behind arched voids of considerable height, would prove consequential for the future