The revolving bridge designed by Leonardo da Vinci was intended for military use. It was thought of to be stable yet portable, so soldiers could transport it and use it again when they were crossing water. Its mechanics consister of pulleys and ropes, and the innovation was on wheels. Da Vinci believed that having mobility was one of the most important things in warfare, so this provided armies with the ability to move quickly and easily get away from the enemy. Image source: Leonardo da Vinci Inventions-Bridges http://www.pathfindersdesign.net/www.pathfindersdesign.net/Leonardo.html