Leonardo's paintings, frescos, architecture and even warfare inventions were all incredible feats of engineering, skill and flare. His meticulous observations and thirst for knowledge based on first hand study, allowed him to find techniques never seen before and hardly seen after. Studying anatomy by dissecting corpses, he was able to translate his knowledge into his paintings and frescos, in the way limbs folded and muscles had to be shaded. His studies in nature gave him inspirations for many inventions and architectural designs. However, all the masterpieces of art and architecture and also all the inventions he put to practice are not for me what defined him as a genius. Outstanding and unique as all those things were, they were made and were delivered by an artist/architect/engineer of special talent. But because they were made they simply were beautiful, innovative yes, probably only possible by Leonardo alone.