The whole system is powered by 14000 horsepower turbines which can pump 200 tons of water a second into the large outlying edogawa river. I'm in the middle of playing Halflife2 right now and something like this looks like its straight out of the game or some sci-fi movie. This unbelievable gallery of photos however, is not CG, it is the real deal.
The site is all in Japanese, but if you click around the menus a bit, there are animations and diagrams of how the system works, and other interesting photos of the high-tech control center and turbine facilities. Supposedly the G-Cans project is also meant to be a tourist attraction, and can be visited for free. very cool. Link