What military vehicle did Leonardo da Vinci design as a covered, round platform with cannon?

Leonardo da Vinci designed an armored vehicle as a covered, round platform carrying cannon.

The vehicle appears in a drawing from about 1487–1489, created while Leonardo was seeking patronage from Ludovico Sforza, ruler of Milan. Its conical cover was intended to protect crew members, while guns placed around the platform could fire in several directions. The design resembles a turtle or a small mobile fort.

The vehicle was to be moved by people or animals operating internal mechanisms connected to wheels. Some modern reconstructions found that the gearing shown in the drawing would not work as expected, possibly because Leonardo deliberately included an error to prevent others from copying the design.

The machine was never built for battle and was not a modern tank. Its importance lies in combining armor, mobility, and all-round firepower in a single concept. The English Wikipedia article often calls it Leonardo's fighting vehicle or armored car.