At every Olympics there is one cycling event that stands out above all the rest: keirin. It's been in the Olympics since Sydney 2000, but it's actually based on a form of track cycling that originated in post-war Japan. Keirin is a gambling sport in Japan, and though it's nowhere near as popular as the national pastime baseball, or held in the same regard as sumo, it is still a multi-billion dollar industry, with races taking place up and down the country on an almost daily basis.