Leonard Da Vinci, following Cesare Borgia to Imola, drew a map of it for military purposes, featuring several innovations that would become commonplace for centuries to come. It is an imaginary aerial view taken from the zenith; the measurements are taken accurately with an ingenious measuring system based on a modified cart with reduction wheels, where the last wheel, with each revolution, releases a pebble into a metal container, also making an audible noise. The map is also easily readable, an important asset on the battlefield.
