Unromantic but true: Great cities don’t just happen; they’re engineered.

Otherwise, Paris might have become the City of Blight instead of the City of Light. In the 1860s, Napoleon III dispatched urban planner Baron Haussmann to draw the clean, efficient edge of modernity over the overcrowded medieval capital. Tenements were demolished, streets widened, gardens planted, sewers installed and more than 20,000 gas lamps erected.