What kind of vehicle did Leonardo da Vinci design with sloped armor and internal gears?

Leonardo da Vinci designed an armored vehicle with sloped armor and internal gears.

The machine appears in a drawing from about 1487 and is often described as an early tank concept. Its conical, turtle-like covering was intended to protect people inside, while several crew members would turn cranks connected to the wheels.

Leonardo’s vehicle was not a practical tank in the modern sense. The surviving design contains a mechanical problem: if the gears are arranged exactly as drawn, the wheels would work against one another. Historians have proposed that this may have been deliberate, an error, or a feature of an unfinished design.

The vehicle also included positions for weapons around its perimeter. It therefore combined protection, mobility, and firepower, but no contemporary evidence indicates that it was constructed or used in battle.