In Isaac Asimov’s Foundation series, the planet Trentor is the capital of the Galactic Empire. Seen from space, Trentor is nothing but city: there are no rivers, trees, or any other natural features, only an endless urban landscape, a metropolis that has taken over the planet. Landing in Mexico City feels like landing in Trentor: the size is overwhelming, and its apparent infinity challenges most people’s understanding of a city. Juan Villoro calls this sensation ‘horizontal vertigo’. The term is borrowed from a description of the grazing lands of the Argentine pampa, and Villoro chose it as the apt title of his chronicle of Mexico City.