Around 4000 BC, the ancient Sumerians invented the sailboat. Sailboats were important as transportation was essential to their culture. The Sumerian civilization flourished because it was able to trade and with other cultures. They set up trade relationships with nearby cities and countries, but since transportation of goods by land routes was hectic and difficult they relied on water transportation for travel and trade. An ancient legend tells that a Babylonian hero endeavored to cross a lake when he was advised by a ferryman to fabricate a punting pole. He fabricated it but he could not use the pole to touch the bottom of the lake. The hero then took off his clothes, stood on his boat, raised his two arms as two masts, and held the clothes over his arms and then the boat sailed along.