Leonardo da Vinci's proposed armored military vehicle was designed to resemble a turtle.
In a drawing from about 1487, Leonardo showed a conical, armored vehicle with sloping sides and a broad circular base. The shape was intended to deflect incoming attacks, while a group of small cannons projected through openings around the perimeter. The vehicle was meant to carry a crew inside and move across a battlefield.
The turtle comparison comes from the machine's low, domed protective shell. It was not a tank in the modern sense: Leonardo's design depended on human-powered mechanisms and did not include an engine, tracks, or a demonstrated prototype.
A famous version of the drawing contains a gearing problem that would make the vehicle move backward if built exactly as shown. Historians debate whether this was an error, a deliberate safeguard, or a copying issue, but the armored concept remains one of Leonardo's best-known military designs.