At the age of 45, Leonardo has reached his artistic maturity, but he still has a dream: to create a great pictorial work.
Due to the outbreak of a plague in Milan, Leonardo draws sketches of an organic city, inspired by blood circulation and organized in channels and streets at different levels so as to ensure the welfare of its inhabitants and the fluidity of the network of roads. He goes to Venice, as a military engineer to design weapons and means of defense against the Turkish invasion. He invents and tests all these weapons but then removes them because he thinks that since they were secret, the enemy had no defense against them. At the request of Cesare Borgia, Leonardo da Vinci left Venice. Borgia appointed him architect and military engineer. Leonardo da Vinci re-invented weapons, but did not make them because he conceived them “as a means of defence against tyranny, not as a means of support”.