Sarushima is the highest point at an altitude of 40m.
There was a lighthouse and a direction center (observation station) equipped with a search light that illuminated a ship navigating the sea at night.
The concrete facility that is currently used an observatory is said to have been the Air Defense Direction Center during the Pacific War.
It is an underground facility with an entrance on the slope and a 2-story building on the ground. Entrance into the facility is prohibited due to its deterioration.