The Blue Pond in Biei is human-made.
*Gasp*
Now enjoy:
About Shirogane Blue Pond in Biei
Location: Shirogane, Biei, Kamikawa District, Hokkaido 071-0235, Japan
GPS map code (for drivers): 796 183 424*87
Website: https://www.biei-hokkaido.jp/ja/sightseeing/shirogane-blue-pond/
What stones are those?