There are many kinds of forts and castles and batteries in Japan. In this thread, I try to show all kinds of Japanese forts and castles and batteries.
The ancient forts: The Imperial Family built some forts in antiquity. Some forts built in antiquity are known nothing about it such as who or when built it. For example: Kinojo(pic) , Kaneda Castle , Takayasu Castle (They are called castle but I think they are fort.)