This war machine designed by Leonardo da Vinci was inspired by the shell of a turtle. This armoured car was to be made of wood covered in metal, and the top was slanted to deflect shots recieved from the enemy. There were cannons around the perimeter of the tank to fire at the enemy from all angles. It was designed to be able to travel in all directions, and be powered by soldiers inside. Scientists today see that there was an engineering flaw in his design, where the wheels would be going in the opposite directions, preventing the tank from advancing properly. It is questioned whether this was a true error, or da Vinci purposely did that to ensure people could not steal his work. Image source: Wikipedia commons, Leonardo da Vinci, design for a fighting vehicle. Image listed as public domain in the United States because it is a photographic reproduction of a public domain work of art.