Cartographic Evidence of Invisible Cities

May 24, 2021


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Barcelona redrawn by air pollution, 2020. Data Source: CALIOPE-Urban (BSC). NO2 episode at 8:00pm, 11 November 2017. © 300.000Km/s.

Visionary evidence

In a lecture Italo Calvino gave about his book Invisible Cities at Columbia University in 1983, he said the following: “I may say that in chapter five, which in the heart of the book develops a theme of lightness that is strangely associated with the theme of the city, there are some of the pages I consider the best as visionary evidence; and perhaps these more ‘slender’ parts, the Thin Cities, are the most luminous areas in the book.”1 In these Thin Cities, subtle cities, Calvino describes the “trading cities” that are cities of nets, spiderweb cities, cities connected by strings; also, he tells us about “cities and eyes”—cities in the clouds where the inhabitants use spyglasses and telescopes to look down at the Earth.

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Centralized, Decentralized, and Distributed Networks from Paul Baran, On Distributed Communications, Memorandum RM-3420-PR, (Santa Monica, California: RAND Corporation, 1964).

Calvino published Invisible Cities in 1972. It was the same year as the first public demonstration of a distributed network for the exchange of information between computers over the telephone network, which would eventually be called the internet.2 A few years earlier, the first image of the Earth was taken from space and broadcast on TV, thanks to TIROS-1, the first low-Earth orbital weather satellite launched by NASA.3

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The first photo of Earth from a weather satellite, taken by the TIROS-1 satellite on April 1, 1960. © NASA.

Since then, the “nets and eyes” that connect and observe Earth from space and from the planet’s surface have only continued to multiply. The internet is now a network of information networks that transmits vast amounts of data, including data from the 2,787 active satellites currently orbiting the planet.4 Forecasts suggest that by 2025 there will be more than 75 billion devices (antennas, cameras, cards, meters, sensors, etc.) connected to the Internet, all of which keep getting smaller, cheaper, and increasingly ubiquitous.5 53.6% of the world’s population has access to the internet, a number that is very similar to the 55% of humans who live in cities. We don’t question the fact that our cities need these “nets and eyes” for their survival, to capture data and transport vital information; we take it for granted, although it has all taken place in just the last fifty years or so. “Visionary evidence” from Calvino, no doubt about it.

Cities and data

Due to this subtle condition described by Calvino as “nets and eyes,” cities are major generators of data—data that provides information about material aspects and also about what is most immaterial. Some of that data is publicly owned. A lot of that data is privately owned. Data becomes information, and information is power—power that companies wield in the cities where they operate. That power has already been denounced by thinkers such as Nick Srnicek in his essay “Platform Capitalism,” Shoshana Zuboff in The Age of Surveillance Capitalism, and Eric Sadin in World Siliconization. It is a power that administrations need to renegotiate with the companies that operate in cities in order to reappropriate that data for the common good.

Access to all this data is complicated. The private data is most often owned by large corporations, and the public data is not always accessible or in a format that can be worked with. We need to renegotiate with the companies that operate in cities in order to gain access to this data. There is data sovereignty, which we must demand from the public sphere, and also the data we can produce from active citizenship. The aim is to redraw the city by creating new cartographies to support the best analysis and diagnosis to resolve our coexistence and guarantee the right to a just city.


We associate cartography with the production of maps that represent the visible world in a synthesized way. These maps have helped those in power control territory for hundreds of years, and more intensely since the colonial periods and the birth of statistics. Mapping in the twenty-first century takes on a whole new dimension. The vast amounts of data that are being captured are mostly invisible to the human eye. The machines that capture, store, and process that data don’t need to see it, but humans do. The data can be presented as statistics and visualized using attractive graphic representations, but in order to study the city we need maps that situate the data in a territory—not only to see the data located at specific coordinates, but to reveal something new that would be impossible otherwise.

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Replica of Container Terminal Remote Operator’s Workspace in #OFFICE, WORK, BODY, LEISURE at Biennale Architettura 2018. © Daria Scagliola.

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Barcelona Center for Traffic Control. © Gunnar Knechtel. Courtesy of the author.

The invisible

Mapping the invisible in the city means putting what is ephemeral on the map. The city is, above all, invisible activity: the data on telephone use, social networks, banking transactions, the consumption of basic supplies, check-ins at restaurants and leisure venues, complaints, etc. and also environmental data such as air quality, water and soil quality, noise pollution, etc. This represents huge amounts of data and metadata.

Metadata is what often gives us the most information. The content of a telephone call isn’t what gives us knowledge about the city; it is the metadata associated with the call, such as geolocation, duration, or roaming, which tells us what places in a city are the most visited by tourists or residents and at what times of day.

But we cannot rely on metadata alone; we need to cross-reference this data with other information to find relevant answers. It isn’t just a question of knowing that the air quality data for one place in the city indicates a concentration of nitrogen dioxide above the maximum air pollution levels recommended by the World Health Organization (WHO). We also need to know where and when that data was collected, on what type of street, what the traffic levels are, what type of population is exposed, their income range, quality of housing, etc. All of this tells us which spaces in the city are most critical to inhabitants’ health. That is the foundation for a change in how cities are designed.

Mapping “the invisible” means mapping everything that we don’t see, everything that has been left off the map. What is it, exactly, that isn’t being mapped? What is it that we aren’t showing that allows systemic inequality, social and environmental injustice to continue?

Evidence as a collective construction

We need evidence because there has been a crime. The crime is the economic system, which, in its most devastating form—neoliberalism—engenders inequality by default and is responsible for our current economic, social, and ecological crisis. We need maps that serve as evidence to help us denounce this situation and propose alternatives.

Constructing cartographic evidence is a political act. Deciding what we consider to be sufficient evidence is also a social construct. This type of cartography is not a mere representation of data; it becomes a presentation of proof. Proof that takes on sufficient authority to question, point out, denounce, to demand responsibilities and changes in the regulations.

In this sense, over the last ten years, prominent research groups from the academic world, agencies, and social movements have been producing cartographic evidence to raise citizen awareness, spark public debate, capture the attention of the media and the courts, and contribute to driving change in public policy.

Community of practice

In 2006, the Spatial Information Design Lab (SIDL) and the Justice Mapping Center in the United States joined forces to rethink the public debate on community justice, spending on incarceration, and social return. They coined the term “Million Dollar Blocks,” based on a map of each prisoner’s home neighborhood and the associated accumulated spending, evoking what that spending could have contributed if it had been invested in education, aid, etc. in those same neighborhoods.6 This methodology has been replicated in different cities in the United States, including Chicago.7

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Million Dollar Blocks, 2006. It cost $11,839,665 to incarcerate people from these eleven blocks in 2003. © Center for Spatial Research at Columbia University.

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Million Dollar Blocks, 2006. It cost $11,839,665 to incarcerate people from these eleven blocks in 2003. © Center for Spatial Research at Columbia University.

SIDL is now the Center for Spatial Research led by Laura Kurgan at Columbia University. The center conceptualizes part of its practices as conflict urbanism: “Conflict is understood, not only as war and violence, but as a structuring principle of cities, as a way of inhabiting and creating urban space.” Identifying which urban conflict requires this cartographic evidence is what makes it a political act. In the case of their project In Plain Sight (2018), they present the anomalies in the population distribution observed in nocturnal satellite images of the Earth, questioning the presumption that the lit areas correspond to cities.8 The project reveals uninhabited illuminated places such as military and other industrial facilities and dark inhabited places such as informal settlements and refugee camps. In Plain Sight is, thus, cartographic evidence of exclusion and expulsion.

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In Plain Sight, [Video Still] 2018. The installation is a collaboration between Diller Scofidio + Renfro, Laura Kurgan, and Robert Gerard Pietrusko with the Center for Spatial Research. The installation was conceived and designed for Dimensions of Citizenship, the US Pavilion at the 16th International Architecture Exhibition of La Biennale di Venezia, commissioned by the School of the Art Institute of Chicago and The University of Chicago.

Forensic Architecture, directed by Eyal Weizman, is a research agency at Goldsmiths, University of London. Since 2011, the agency has been investigating human rights violations—including violence committed by states, police forces, armies, and corporations—by using spatial and architectural analysis, open-source research, digital modeling, and immersive technologies, as well as desk research, interviews, and academic collaborations. In their work, the creation of maps is one of the fundamental tools to situate criminal events spatially. Forensic Architecture calls this type of mapping tool counter-cartography: “If the map of cartography is used as an instrument of domination, then in a counter-cartography way, it can also be used to expose this reality and resist it.”9 A recent example is the project “Police Brutality at the BLM protests” which mapped police brutality during the Black Lives Matter protests in various North American cities.10 These new urban maps revealed patterns and trends from the months of violence, including the use of tactics such as corralling, “kettling,” and interactions between officers and members of militias and extreme right hate groups. This cartographic evidence is being used to support legal actions denouncing these police practices and demanding they be abolished.

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Police Brutality at the Black Lives Matter Protests, 2020. © Forensic Architecture.

The Anti-Eviction Mapping Project (2014-present), cofounded by Erin Mc Elroy, is a critical cartography project and a collective multimedia storytelling effort to document dispossession and resistance to gentrified urban landscapes. It is a collectively authored mapping project produced by volunteers working primarily in the San Francisco Bay Area, Los Angeles, and New York City. The Anti-Eviction Mapping Project (AEMP), was formed at the height of the San Francisco Bay Area “Tech Boom 2.0” when real estate speculation and local and state policies led to growing rates of foreclosure, eviction, and displacement. The AEMP was formed to provide analysis, resources, and documentation that could be used by local organizations and activists in their fight against gentrification. Based on the experience in San Francisco, the AEMP works in solidarity with organizations that defend access to decent housing worldwide, providing tools for resistance and platforms for building new movements.

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AEMP (Anti-Eviction Mapping Project), San Francisco Map, 1994-ongoing. © Anti-Eviction Mapping Project.

Mapping for Change is a subsidiary agency of UCL London, cofounded by Muki Haklay, which develops tools and online mapping platforms, and offers support to communities following citizen science methodologies, so that citizens are empowered through the use of collective mapping to demand improvements in their environment.11 One of its most compelling projects is air pollution mapping. This methodology has been extrapolated to various cities, including Barcelona. In 2018, the xAire project was carried out with the collaboration of the Open Systems research team at the University of Barcelona. Contacting with the associations of families of students from eighteen schools, they managed to recruit 1,680 volunteers to install more than 725 NO2 sensors. The resulting map is the cartographic evidence of the impact of pollution on the environments around the schools involved in the project. In 2021, there are now fifty schools staging demonstrations on Friday afternoons to demand healthy and safe school environments—that is, with clean air, no traffic, and more green spaces.

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Community map showing the results from community based air quality monitoring of nitrogen dioxide. All monitoring is undertaken using diffusion tubes. Project developed within the Estació Ciutat initiative.

The MIT Civic Data Design Lab, led by Sarah Williams, partnered with the AIA New York and the Center for Architecture to create “Visualize NYC: 2021.”12 They developed a series of maps to help highlight the problems affecting the city: how the pandemic has changed street activity (Evolution of Public Space), vulnerability to heat in the city (Climate Change and Resilience), the rent burden with respect to residents’ income (Right to Housing), and the interaction of demographic, socioeconomic, environmental, and health factors (Public Health). The project is intended to create public awareness in order to generate the necessary support to request changes in public policies.

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To help make sense of the future of New York’s built environment and the role the 2021 election will play, the Center for Architecture and MIT’s Civic Data Design Lab (CDDL) have teamed up for Visualizing New York: 2021, an exhibition that will use data visualizations to explain these pivotal topics, and provide New Yorkers with the information they need going into one of the most important election seasons of the past few decades. © Center for Architecture and MIT’s Civic Data Design Lab7.

The team at 300.000 Km/s, led by Mar Santamaría and Pablo Martínez and based in Barcelona, began their career in 2013 with the atNight project, visualizing the nighttime activity in the city of Barcelona based on data, much of it gathered from social media. At that time, it offered a very revealing portrait of the city, which anticipated what the analysis of mapped data could offer. In 2016, they received multiple awards for the “Ciutat Vella Land Use Plan,” an innovative mapping project that brought about a shift in public policies.13 It began with residents’ demands for a solution to noise pollution and reports from neighborhood public health centers on chronic insomnia and stress in people of all ages, especially in children and the elderly. In response to the urban conflict, the administration commissioned a diagnosis that took the form of a Data Atlas. It is an Atlas of 200 maps created using the data from traditional urban planning: urban morphology, cadastre, cartography, and statistics. In addition, the maps incorporate public data of a kind that has never been used in urban planning before, such as noise level meter readings, complaints to the city police, complaints to the City Council IRIS System, data from the Autoritas inspection system, data from Barcelona’s energy agency (routes defined for cleaning crews, etc.), data from the district activity licensing department, etc. This was combined with data from private companies such as BBVA bank cards, Fotocasa, Inside Airbnb, Twitter, Instagram, Cellnex Wi-Fi antennas, and Google Places, among others. All this data made it possible to map behavior in the city during the day, at night, and at daybreak, in order to create cartographic evidence, which citizens were then able to use in order to demand a new Land Use Plan for the district that would prioritize the health of the community, the common welfare, and acoustic comfort above private economic interests.

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Noise and bar capacity complaints. Atlas of the Ciutat Vella of Barcelona, 2017 © 300.000Km/s.

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Ciutat Vella Land Use Plan, 2018. © 300.000Km/s.

Visionary cartographic evidence

With all these examples, we see that by using data we can build tools such as cartographic evidence that can have an impact on an increasingly complex reality. Cartographic evidence is an essential tool to highlight and contribute to conflict resolution. Because a “smart” city is one in which citizens use data to diagnose its problems. It is urbanism using big data for the common good as a tool to uphold the social contract, a tool that complements citizen participation.

We cannot continue working the way we used to. Given these precedents we need a cultural shift and a professional methodological shift among the collective of architects and urban planners.

– We need to update the profession of urban planner with more specialization in schools of architecture and urban planning and continuing professional development.
– We need the administration to understand these new methodologies, new methods of planning in the consolidated city.
– We need the administration to issue contracts in keeping with these new innovative methodologies with more dignified hiring practices.

And to make all this possible,
– We also need a citizenry and an administration that defends data sovereignty for the common good as the foundation of an urban planning for the common good.

“The city will belong to those who map it” is one of the statements I have read repeatedly from 300.000 Km/s. Here, I would add that the city will belong to those who collectively construct the cartographic evidence necessary to renew the social contract that will allow us to live together and survive in a just society. At a time when fake news has become widespread and sectors of power persist in denying the crimes that are committed, the creation of evidence is a fundamental tool for citizens to combat exploitation, systemic inequality, and mass surveillance by governments and corporations. There is an urgent need to produce cartographic evidence to offer to the public sphere as a tool to renegotiate the social contract. Collective bargaining is what sets the parameters of sufficient evidence. We need to be visionaries and have foresight; like Calvino, we need to make invisible cities visible, this time not with text but with cartographic evidence.

This text is part of the ongoing Nocturnal Landscapes: Urban Flows of Global Metropolises initiative. The project provides a comprehensive look at global metropolises at night, combining analysis and observation, questioning the correlation of human activity and light, and revealing hidden aspects of our cities.

This text has been supported by the Barcelona City Council – Institut de Cultura de Barcelona.

1 Italo Calvino, “Italo Calvino on ‘Invisible Cities,’” Columbia: A Journal of Literature and Art, no. 8, (1983): 37–42. Accessed January 19, 2021.
2 Donald Davidson, “A Brief History of the Internet,” ACM SIGCOMM Computer Communication Review 39(5): 22-31. Accessed May 24, 2021.
3 “First Photo of Earth From a Weather Satellite TIROS-1,” NASA, April 2, 2009.
4 Therese Wood, “Who owns our orbit: Just how many satellites are there in space?,” World Economic Forum, October 23, 2020.; See also: “UCS Satellite Database,” Union of Concerned Scientist, December 8, 2005, Updated January 1, 2021.
5 “Internet of Things (IoT) connected devices installed base worldwide from 2015 to 2025,” Statista, Accessed May 24, 2021.
6 Center for Spatial Research, “Million Dollar Blocks,” Accessed May 24, 2021.
7 Daniel Cooper, Ryan Lugalia-Hollon, “Chicago’s Million Dollar Blocks,” Accessed May 24, 2021.
8 Diller Scofidio + Renfro, Laura Kurgan, and Robert Gerard Pietrusko with the Center for Spatial Research, “In Plain Sight,” Accessed May 24, 2021.
9 “Space is an optical device that helps us to make sense of the present,” European Cultural Foundation, April 19, 2018.
10 Forensic Architecture, “Police Brutality at the Black Lives Matter Protests,” Accessed May 24, 2021.
11 María Alonso, “Biggest Air Quality monitoring action in Barcelona inspired by MfC methodology,” Mapping for Change, 20 February 20, 2018.; See also, “xAire”
12 Civic Data Design Lab in collaboration with AIA New York and the Center for Architecture, “Visualize NYC 2021,” Accessed May 24, 2021.
13 300.000 km/s, “Ciutat Vella,” Accessed May 24, 2021.