Koyama was once a castle town of the Kimotsuki Clan, who had ruled most of Ohsumi region for nearly 600 years before surrendering to the Shimadzu clan of Satsuma in late 16th century.
About a ten-minute drive from downtown Koyama lies a little mountain which actually was the site of Lord Kimotsuki’s headquarters. It is considered to be one of the most precious medieval mountain castles in Japan, which is visited by scholars and historians from time to time.
However, there are no signs of an actual castle in the mountain. What you see are only signposts which indicate the various functions of the castle. Maybe because of that, it is a place to inspire your imagination. You could imagine that in the old days this is where samurai used to live.
Nearby the castle is the Doryuji Temple, which was built by a Chinese Zen Buddhist monk in the 13th century. It is believed that the temple was commissioned by one of the Kimotsuki lords.