Sakihama Oyster Fossil Bed
The Sakihama Oyster Fossil Bed and Tunnel Tombs formed approximately 120 to 130,000 years ago when this area was at the bottom of the ocean. This oyster shell bed was shaped by the exposure of geological formations deposited with fossil oyster shells. During the late Kofun period between the 6th and 7th century AD, this place was used as tunnel tombs dug into the slopes. A total of 17 tunnel tombs were discovered in various types, including tombs with only a main area for the coffin, while other tombs had three parts in the front and two sides.
Because it is near Ring Ring Road, it's a great place to visit while cycling if you're interested in Japanese history.