Giorgio Vasari, Leonardos first biographer, said that the artist used to sketch many designs for architecture. In fact, in the so-called letter of employment written to Ludovico il Moro in 1482, Leonardo presented himself as a military engineer, able to satisfy the demands of the Duke of Milan in peace and in war, declaring that he can give perfect satisfaction and to the equal of any other in architecture and the composition of buildings public and private. And then he speaks of his ability in hydraulic engineering for conducting water from one level to another. Leonardo studied in depth several ancient texts but also the