What protective structure did Leonardo da Vinci design with sloped sides and a conical roof?

Leonardo da Vinci designed an armored vehicle with sloped protective sides and a conical roof to shield soldiers in combat.

The vehicle appears in a drawing from about 1487–1489. Its circular platform was covered by armor plates and carried light cannons around the perimeter. The sloping armor was intended to deflect projectiles, while the crew would operate the vehicle from inside. The design is commonly compared with a modern tank because it combined armor, mobility, and mounted guns.

Leonardo’s vehicle was not a functioning tank. It depended on manpower and could have been difficult to move, especially because the gearing shown in the drawing appears problematic. Some historians have suggested that the apparent gear arrangement may have been deliberate or may reflect an error in the design. The vehicle is best understood as a Renaissance siege-machine concept rather than a direct modern tank prototype.