This volume is the first book-length study of Leonardo da Vinci's Sforza Monument Horse, which was designed in the 1480s as a colossal bronze equestrian monument to Francisco Sforza, the duke of Milan, but never executed. At twenty-four feet in height, the Sforza Monument would have been the largest equestrian statue ever made. During his seventeen years in Milan, Leonardo researched the project intensively, making scores of drawings of horses and technological studies for its casting. He prepared the clay model and molds for the great horse and invented a novel technique for its fabrication, but with the fall of Sforza from power in 1499, the bronze colussus, recognized in its own day as a symbol of the master's genius, was never cast. Illustrated by 87 black-and-white plates, this study reevaluates this great project 500 years after its genesis.