Oya Museum displays Oya stones collected for 70 years between 1919 and 1986 as well as a large, former underground quarry. At the museum, you can experience and learn various things including the history of Oya stone mining. The former underground quarry is 20,000 square meters and 30 meters deep which is large enough to have a baseball field inside. You can see the traces of pick-axes on stone surface and feel the history of the mining era. The scenery reminds you of an enormous underground structure that is absolutely amazing.