Leonardo's Horse

Leonardo's Horse is a project for a bronze sculpture that was commissioned from Leonardo da Vinci in 1482 by the Duke of Milan Ludovico il Moro, but never completed. It was intended to be the largest equestrian statue in the world, a monument to the duke's father Francesco Sforza. Leonardo did extensive preparatory work for it but produced only a large clay model, which was later destroyed.

About five centuries later, Leonardo's surviving designs were used as the basis for sculptures intended to bring the project to fruition.

Source: Wikipedia