"Super-Kamiokande is the large water Cherenkov detector. The construction was started in 1991 and the observation began on April 1, 1996. The Super-Kamiokande is operated by an international collaboration of about 110 people and 30 institutes from Japan, the United States, Korea, China, Poland and Spain.
The Super-Kamiokande detector consists of a stainless-steel tank, 39m diameter and 42m tall, filled with 50,000 tons of ultra pure water. About 13,000 photo-multipliers are installed on the tank wall. The detector is located at 1000 meter underground in the Kamioka-mine, Hida-city, Gifu, Japan..."
http://www-sk.icrr.u-tokyo.ac.jp/sk/index-e.html