The eastern part of Kagawa Prefecture, Higashi-Kagawa City found many geological treasures.
The Kinujima Columnar Joint has several layered pillars of basalt, which is a rare geological feature and the local people believe that the deity Ryujin resides here. During times of low tide, Kinujima Island is connected to Marugamejima Island by land, and the island also featured a black and white striped lamprophyre rock called Kaburakoshi. These features are designated a Natural Monument by the Japanese government. You can explore the area by sea kayak tours, motor boat, or stand-up paddleboard.