Kaerimizu is the largest “uvala” in east Akiyoshidai. Uvala is a limestone basin, formed by the merging of numerous sinkholes. You can observe the fusulinid fossil at Kaerimizu Uvala as well.
At the bottom of the uvala in Kaerimizu, there is a stream less than 20 meters long running between the two holes, one is where the water comes out and the other is where the water sinks in. The stream is unique to the limestone landforms and is the only river recognized in Akiyoshidai.
Kaerimizu Uvala is also famous for its contribution to geology. Dr. Yoshiaki Ozawa, the geologist from Tokyo Imperial University (today’s Tokyo University), discovered the inverted stratum of earth at Kaerimizu Uvala, which later contributed to the formation theory of the Japanese island chain.