Super-K !

The Super-Kamiokande (full name as Super-Kamioka Nucleon Decay Experiments) is a neutrino observatory near the city of Hidu, Japan. It's located more than 3,200 feet underground. Contained in a stainless steel tank more than 135 feet tall and 128 fee in diameter, are almost 14,000 photomultiplier tubes, to record the very occasional interaction of a neutrino, with an atom in a molecule of the more than 50,000 gallons of ultra-pure water with which the tank is filled.

Here is an very cool photograph of the tank being filled, complete with a boat with two technicians in it... click on the photo for full image.
PS: the light shining on the underwater photomultipliers, reminds me greatly of Monet's 'Water Lily' series of paintings...