This festival dates back to the 16th Century when large kites were flown in celebration of the birth of a baby son to the Lord of Hamamatsu Castle. Even today, kites are flown at Hamamatsu when a baby boy is born, a custom known as hatsudako. On May 5th, a festive day to pray for boys' good health and a bright future, it is the custom in Japan to fly decorations called koinobori, which are carp-shaped streamers. Carp are known to swim up waterfalls and this powerful image of the carp overlaps with the image of advancing in one's career. In Hamamatsu City, koinobori are displayed in a grand style, with the carp streamers flying on wooden poles as tall as 10 meters.