Iwaya castle ruins sits within Onojo fortress ruins. Onojo fortress dates back to the 7th century making it probably the oldest fortification in Japan. Iwaya castle dates back to the 16th century. Finding information about Iwaya castle has been virtually impossible. I searched both Japanese and English. However, I must say on thing that really… Read More Iwaya castle ruins-Shimazu and Toyotomi samurai battles. Fukuoka, Kyushu.