example, he decorated some room in the duke's palace and even devised a system for supplying and heating the water for the duchess's bath. One of Leonardo's most challenging projects was the creation of a grand monument to commemorate Ludovico's father. After working on it for over a decade, he finally completed an impressive clay model of a rider on a horse. It is believed to have stood more than seven meters high. A great deal of bronze was required to cast the statue according to his plan. In the end, however, the statue was not built because the duke decided to use the bronze to make weapons. Since the clay model was destroyed by the French after their invasion of Milan,the only evidence left of this legendary sculptural project today is an assortment of sketches in Leonardo's notebooks.