Leonardo da Vinci was obsessed with water. The famed Italian Renaissance artist meticulously drew every aspect of rivers, from the nature of water drops to the ways currents create and destroy the earth’s surface. His obsession led him to become a professional hydraulic engineer and an expert on the physics of water. He disproved Aristotle’s 1,800-year-old theory of the water cycle and developed the one we use today. He discovered the nature of erosion and heretically disproved the biblical flood. He created beautiful maps and drawings of river currents and of his audacious plans to reroute the Arno River for war and peace.