Forget CERN, the science fiction is here (compare with the movie Event Horizon): Super-Kamiokande, a neutrino observatory built 1993-1996 and located under Mount Kamioka in Japan. The observatory is designed to search for proton decay, study solar and atmospheric neutrinos, and keep watch for supernovae in the Milky Way Galaxy. The Super-K is located 1,000 m underground and consists of a cylindrical stainless steel tank that is 41.4 m tall and 39.3 m in diameter holding 50,000 tons of ultra-pure water.
Check out the website for more details and more pictures.
credit: Kamioka observatory, ICRR