De Architectura (On Architecture), written by the Roman engineer Vitruvius around 15 BCE and dedicated to the emperor Augustus, is a treatise in ten books covering building, engineering and town planning. Its first book addresses the siting of cities, the choice of healthy ground, the avoidance of harmful winds through street orientation, and the layout of an ideal town within radial, octagonal walls. Vitruvius also set out his famous triad of firmitas, utilitas and venustas — durability, usefulness and beauty. The work drew together Greek and Roman practice into a systematic account.
It is the only substantial planning and architectural treatise to survive from classical antiquity, and its rediscovery in the fifteenth century made it the foundation of Western architectural and urban theory. Renaissance ideal-city designs drew directly on its principles of siting, geometry and proportion.