'What does the world look like from the moon?''How do our bodies work?''Is it possible for people to fly?''Can I make a horse of bronze that is 8 metres tall?''How can we have cleaner cities?' All his life, Leonardo da Vinci asked questions. We know him as a great artist, but he was one of the great thinkers of all time, and even today, doctors and scientists are still learning from his ideas. Meet the man who made a robot lion, wrote backwards, and tried to win a war by moving a river . . .