Certeau discusses his essay "Walking in the City" from his book The Practice of Everyday Life. In it, he elaborates on the analogy between urban systems and language, likening improvisational walking through a city to turns of phrase, inside jokes, and storytelling. He also describes seeing Manhattan from the 110th floor of the World Trade Center, where the urban island appears as a sea within a sea, with its skyscrapers, parks, and neighborhoods undulating into the distance in a "wave of verticals" that represents the extremes and contrasts of the city.