On September 7, 2009, Mexico City awoke in the midst of floodwaters. Nearly 700 years after the Aztec founded their island city of Tenochtitlan in 1325 (renamed Mexico City by the Spanish), it has yet to solve its flood problems. Mexico City is a special case in urban history because the measures taken to avoid inundations have fundamentally changed this city’s character. In 1521, it was an island-city; in 1629, it lay near the banks of the Lake of Mexico; and by 1700, it rested on reclaimed land. This transformation is significant, speaking not only to the flood control approaches of the Aztec and Spanish, but equally important, to how these methods profoundly altered this city’s urban condition. Like the Aztec, the Spanish sought to control the six fresh- and salt-water lakes surrounding the city to prevent inundations, yet their approach was quite different. The Aztec model relied on containment and regulation, while the Spanish undertook drainage, referred to as the desagüe. Despite the scholarly attention devoted to pre-Columbian and colonial hydraulics and this city’s urban form, no comprehensive research examines the relationship between the city’s lacustrine environment and its form. The Hydrographic City addresses three key questions: (1) What were the respective flood control approaches of the Aztec and Spanish? (2) How did these approaches shape two fundamentally different cities? (3) How did the Aztec and the Spanish differ epistemologically in how they conceived of their respective cities’ aquatic conditions?