Title: The 99% Invisible City A Field Guide to the Hidden World of Everyday Design

Author: Roman Mars and Kurt Kohlstedt

Completed: November 2025 (Full list of books)

Overview: I’ve been listening to the 99% Invisible podcast for over a decade and when they released this book, I had to read it. When I got it, hardcover was the only option and my system for taking notes works best with ebooks so when they announced that we’ve hit the fifth anniversary of its release, I decided it was time to revisit it. Much of it I remembered but several of the stories felt new again.

The podcast helped me realize that everything can be interesting if you dig deep enough into it. This book dives into several topics that were more difficult to cover without visuals and gives insights into what’s happening just below the surface of the city. Since reading it, I’ve noticed several Thomassons and started paying attention to the different colors of paint on the roads while running and biking.

Highlights:

• On city streets today, you can see the spectrum of safety colors that have been formalized and revised over the decades by the American National Standards Institute: RED: electric power lines, cables, and conduit ORANGE: telecommunications, alarm and signal lines YELLOW: gaseous or combustive materials including natural gas, oil, petroleum, and steam GREEN: sewers and drain lines BLUE: potable water PURPLE: reclaimed water, irrigation, or slurry lines PINK: temporary markings, unidentified facilities, or known unknowns WHITE: proposed excavation areas, limits, or routes
• Even though they are generally positioned at eye level directly adjacent to entryways and are adorned with reflective red stripes, Knox Boxes are easy to overlook. Like Kleenex, Dumpster, or the once-trademarked escalator, Knox Box is the common brand name associated with a generic thing: in this case, the rapid entry access boxes affixed to all kinds of urban architecture. When disaster strikes, these urban safes go from being functionally invisible to highly essential in an instant. Seconds count in an emergency, so getting inside a building quickly and safely is critical. Knox Boxes offer a simple solution: when emergency personnel respond to a call and arrive on site, they use a master key or code to unlock a rapid entry access box and retrieve its contents. Inside a typical box is another key or code for accessing that specific building.
• Genpei Akasegawa noticed an oddly useless staircase alongside a building. A few steps led up to a landing, but there was no door at the top where he would have reasonably expected to see one. What struck him as particularly curious, though, was that the railing running along these stairs to nowhere had been recently repaired. Despite serving no function, the stairs were apparently being kept in working order.
• Thomassons are also delightful to find, so one could argue that the association isn’t as negative as it might seem at first. Thomassons are treasures waiting to be discovered and analyzed—whether or not they are art, they are an intriguing lens through which to look at and understand change over time.
• Meanwhile, fake metal trees were put up next to a popular bridge in Moscow to give people an alternative place to attach locks. Approaches like this echo the treatment of graffiti in some cities where special mural-making walls are presented as alternatives to illegal vandalism. Like kissing the Blarney Stone in Ireland or sticking a wad of gum on a rather gross wall in Seattle, putting up a lock may seem like a novel lark, but when a lot of people line up to do the same thing, such traditions can lose their romantic appeal.
• Converted cannons can still be found sticking out of streets and sidewalks around Britain, often serving as traffic barriers or survey markers. Around the world, people pass by cannon bollards all the time—these stalwart remnants can be found shielding building corners in Halifax, Nova Scotia, and protecting pedestrians from cars along the sidewalks of Havana, Cuba.
• There are five key principles of good flag design according to Kaye, many of which can also be applied to all kinds of other designs: (1) keep it simple, (2) use meaningful symbolism, (3) use two or three basic colors, (4) no lettering or seals, and (5) be distinctive or be related. In other words, a good city flag should be simple but memorable, easy to recall, and usable at different scales.
• “if you had a good city flag you would have a banner for people to rally under to face those more important things.” Bad city flags go unused, ceding visual branding territory to sports teams and corporate interests, which come and go. When city flags are done well, they are remixable, adaptable, and powerful long-term tools for civic engagement as well as sources of local pride.
• Marr explained that he had read it on a plaque prominently placed right outside the building where he was speaking and that his motto is to “always read the plaque.” It’s a mantra that has an obvious literal meaning, but it’s also another way of reminding ourselves to constantly be on the lookout for stories embedded in our built environments.
• In James Loewen’s book Lies Across America, the author points out that historical markers often say as much or more about the era they were dedicated in as they do about the specific times, places, and people they are ostensibly there to commemorate. Many markers in the American South that whitewash slavery are very much products of the turn of the twentieth century when the backlash against progressive Reconstruction was in full force.
• The vast majority of the graphic designs crowding your visual field are advertisements. It’s probably okay to ignore most of them.
• business leaders with vested interests in their ad space fought back. Corporate lobbyists argued the ban would be bad for the economy and compromise real estate values. They also tried to appeal directly to everyday citizens whose taxes might have to pay for removing old posts that would no longer be supporting billboards. There was even an argument that illuminated ads helped people to safely navigate the city streets at night. Clear Channel Outdoor, one of the world’s biggest outdoor-advertising companies, went so far as to sue the city, claiming the ban was unconstitutional.
• The Civil War’s unprecedented death toll also helped inspire another great innovation of the US Postal Service: home delivery. It was too painful and personal for mothers and wives to receive news of the death of a loved one in public post offices, so mail carriers started delivering letters directly to families so they could read the bad news in the privacy of their own homes.
• Presented with wide open spaces, drivers will go faster. Intentionally closing off space by adding trees and other landscaping along the side of the road may make a driver a little more anxious but also more cautious, which can in turn make roadways that much safer for everyone.
• Peter Norton recounts in his book Fighting Traffic, cars began to be viewed as harbingers of death. One newspaper cartoon of the era depicted a car as a toothed monster being worshiped on a pedestal, framing it as a modern Moloch—a polemical automotive-age resurrection of an ancient biblical deity associated with child sacrifice.
• There are many variants of traffic-calming designs out there, including pinch points, chicanes, gateways, and various other kinds of raised pavements and curb extensions. Suffice it to say that urban designers have tried a lot of tricks to slow drivers down.
• When it comes down to it, the trust that people put in the security of most entryways is now once again less about the lock itself and more about faith in a broader social order that respects the division between public space and private property.
• Following Otis’s death in 1861, his sons iterated on their father’s invention and began marketing it more aggressively to the public. They targeted hotels, convincing them that with a fancy elevator in place, rich guests could quickly ascend to the top floors and escape the noise and bustle on the first level. Historically, the ground floor was the most accessible and thus the most desirable, but it didn’t have to be, they argued.
• London has used a roundabout and statue at Charing Cross as a central point of reference to measure certain distances. Metropolitan police initially served only neighborhoods within a radius of twelve miles from Charing Cross, and hansom cab drivers were obliged to take fares only up to a fixed distance from that central point. Today, London cab drivers are still tested on their knowledge of an area six miles in any direction from Charing Cross.
• Some of these places are clearly designed, like gores or berms, but they are often overlooked. Most of these spaces, though, are leftovers in planned areas that were created incidentally through the process of car-centric urban development.
• For the markers left behind in San Francisco, though, this wasn’t the end of the story. Many individual headstones from old graveyards ended up being reused as building material around the city. Intact headstones and fragments of them can be found all over San Francisco. Some wound up at Ocean Beach, arrayed to reduce coastal erosion, while others ended up in Buena Vista Park, lining trails and gutters.
• There are numerous design strategies and technologies aimed at keeping these feathered nonfriends from occupying urban spaces and outdoor surfaces, including spikes, wires, netting, and even miniature electrified fences. Such innovations largely fail to do what they are designed to do, though. They mostly just move pigeons around, pushing the birds to adjacent structures.
• It was Modernists like Le Corbusier who favored rectilinear steel, glass, and concrete forms that in turn made cities perfect places to skateboard. “Modernists were the ones that reinterpreted a bench in a park as a slab of granite,” Bracali notes, adding that this design paradigm involved a turn away from “flowing landscapes [with] grassy areas” toward “paved open plaza spaces,” which produced great surfaces, ledges, and edges for skateboarders.
• Given the long history and modern prevalence of defensive designs, the outrage and days of protests against Tesco’s spikes took the company by surprise. Subsequent criticism of anti-homeless spikes around London reached a crescendo when then-mayor Boris Johnson called them “ugly, self-defeating and stupid,” which arguably also describes certain British prime ministers.
• In the 1700s and 1800s, revolutionaries would smash them in order to move around more freely in the shadows. During the French Revolution, the tables were turned and some lampposts were used as gallows for hanging officials and aristocrats, leading to the French phrase “À la lanterne!” (“To the lamppost”), a call to execution akin to “String ’em up” in English.
• When the sweeping Americans with Disabilities Act of 1990 was hung up in the House of Representatives, disabled demonstrators left their wheelchairs and crawled up the marble steps of the Capitol building to make sure the bill was passed by physically demonstrating the challenges they faced in a built environment that excluded them.
• Mariño came to see bicycle rights as civil rights. For him, cycling embodied individuality as well as “women’s rights, urban mobility, simplicity, the new urbanism, and, of course, environmental consciousness.” Having also been exposed to protest culture in the United States, Mariño organized local cyclists to put up signs and get permission to temporarily close two major streets, leaving them open for cyclists and pedestrians. Thus, the first Ciclovía was born, and from there, its influence spread. Four decades later, on Sundays and public holidays, a vast interconnected network of Bogotá’s streets is shut down to automotive traffic, creating an extensive “paved park” for runners, skaters, and cyclists.
• These weekly Ciclovía events draw as many as two million people out into the streets—about a third of the city’s population—to enjoy the seventy-plus miles of repurposed road space.
• The problem, as he sees it, is that citizens are used to cities being car-centric. “People have internalized that that is how cities look and so assume that’s normal . . . that the streets are dedicated to cars.”
• “We must first remember that all cities were car-free little more than a century ago,” writes Carfree Cities author J. H. Crawford. “Cars were never necessary in cities and in many respects they worked against the fundamental purpose of cities: to bring many people together in a space where social, cultural and economic synergies could develop. Because cars require so much space for movement and parking, they work against this objective [by causing] cities to expand in order to provide the land cars need.”