What type of vehicle did Leonardo da Vinci design with sloped armor and cannon ports?

Leonardo da Vinci designed an armored vehicle with sloped armor and cannon ports.

The vehicle was conceived as a heavily protected fighting machine, often described as an early tank. Its conical, turtle-like covering was intended to deflect incoming projectiles, while openings around the sides allowed cannons to fire outward. The drawings also show wheels and an internal mechanism for driving the vehicle.

Leonardo prepared the design in the late fifteenth century while seeking military employment. The concept was ambitious, but it was not produced as a battlefield vehicle in his lifetime. A well-known drawing appears to contain a gearing arrangement that would make the vehicle difficult or impossible to drive as shown.

Some historians interpret that flaw as an error, while others have suggested that Leonardo may have included it deliberately to prevent the design from being copied. Whatever the reason, the machine should be called an armored vehicle rather than a modern tank, since it lacked an engine and was never operationally deployed.