第二次世界大戦中、館山海軍航空隊によって建設された未完成の防空壕跡で、全長1.6kmあります。証言によれば、内部には発電所跡だけでなく、事務所、病院、電信室、倉庫などがあったとされています。壕内では地層の重なりや地層の変動現象など貴重な地質遺産が観察されます。

During the Second World War, an unfinished air-raid trench was constructed by the Tateyama Naval Air Corps, measuring a total length of 1.6 km. According to testimonies, the interior not only includes the remnants of a power station but also features offices, hospitals, telecommunication rooms, warehouses, and more. Within the trench, valuable geological heritage such as overlapping layers and displacement phenomena of the strata can be observed.