S P O T ／ SPOT-217

Kamioka Mine Ruins / Mozumi Pit (Super-Kamiokande Site)

神岡鉱山跡・茂住坑かみおかこうざんあと・もずみこう

An industrial site with documented extraction records dating to the Nara period (c. 720 CE), the Kamioka Mine operated as Japan's largest zinc, lead, and silver producer under Mitsui Metals management from 1874 until cessation of ore extraction in 2001. Total ore processed over the modern period reached approximately 75 million tonnes. Following closure, the Mozumi pit — situated approximately 1,000 m below the mountain surface — was converted into the installation site for Super-Kamiokande, the University of Tokyo's Institute for Cosmic Ray Research neutrino detection facility and, at the time of its commissioning, the world's largest water Cherenkov detector. Super-Kamiokande data contributed directly to the 2015 Nobel Prize in Physics awarded to Dr. Takaaki Kajita for the discovery of neutrino oscillations. The mine's exceptional rock overburden minimizes cosmic-ray background noise, while stable underground temperatures (13–14°C year-round) and abundant groundwater (used as ultra-pure water in the detector) made the site uniquely suited for the experiment.