Muroya Cave is located on the Muroya River, upstream of the Tokonami River at an altitude of 218m; the cave is about 3m high, 7m wide and 8m deep. An outcropping of rhyolite eroded on the left bank of the Muroya River and created the cave.
Kozaburo Nakamura of the Nagaoka Municipal Science Museum and Tamotsu Ogata of the Anatomy Class, School of Medicine, Niigata University excavated the site from 1960–1962.
They found stone tools consisting mainly of earthenware that established the beginning of the oldest stage of the Jomon period, and also excavated flint arrowheads and scrapers. Together with Kosegasawa Cave this cave is an important site for researching the beginning of the Jomon culture. Buried human bones from the early Jomon period, the oldest human bone material in the prefecture, were found, making this cave invaluable to understand the relationship between caves and burials in those days.
The excavated materials were designated as important cultural property of Japan in 2000; they are housed and exhibited in the Nagaoka Municipal Science Museum.