Tokyo's G-Cans Project
Link - The G-Cans Project is a massive project, begun in Tokyo 12 years ago, to build infrastructure for preventing overflow of the major rivers and waterways spidering the city (a serious problem during rainy-season and typhoon season). The underground waterway is the largest in the world and sports five 32m diameter, 65m deep concrete containment silos which are connected by 64 kilometers of tunnel sitting 50 meters beneath the surface.
The whole system is powered by 14000 horsepower turbines which can pump 200 tons of water a second into the large outlying edogawa river.
The site is all in Japanese, but offers an ubelievable photo gallery (no translation needed). Supposedly the G-Cans project is also meant to be a tourist attraction, and can be visited for free. (And, remember, my birthday is fast approaching on Dec. 3. If you haven't gotten a present yet, feel free to fly me to Tokyo to see the G-Can Project.)