Unbelievably Cool Research Facilities

Super Kamiokande detector, Kamioka Observatory, Japan.
An old favorite on the inter tubes, this 50′000 ton cylindrical ‘ring-imaging water Cerenkov detector’ can be found at the Kamioka Mozumi mine in Japan - 1′000m underground. clever people built the machine to detect neutrinos, proton decay and cosmic rays: this is done using the 12′000-ish photomultiplier tubes (extremely sensitive light detectors) visible on all walls of the ‘ultra-purified water-filled’ tank. LINK