Leonardo da Vinci designed his armored vehicle to resemble a tortoise.
The vehicle, drawn around 1487–1489, has a conical armored shell that slopes upward toward a central turret. Its low, rounded profile was intended to protect occupants from enemy fire while giving the machine a broad field for mounted weapons. The shape is commonly compared with a tortoise because the shell covers the vehicle and its crew.
Leonardo proposed that the vehicle be moved by several men turning cranks connected to wheels. Although often called a tank, it was not a functioning modern tank: it had no engine, no demonstrated battlefield performance, and no reliable system for steering or propulsion.
One famous drawing appears to contain a flaw that would make the mechanism move backward. Historians debate whether this was an error, a copying issue, or an intentional safeguard. In any case, the design remains an influential early concept for an armored fighting vehicle.