Shiki Castle was the home castle of the Shiki clan, which governed the northern half of Shimo-amakusa for around 400 years from the Kamakura period to the Azuchi-Momoyama period. The main parts of Shiki Castle were Honmaru (the center compound), Ninomaru (the secondary compound), Demaru (a tower built onto the castle and used for attack and defense), and a baba (a riding ground). To the south, it had a tatebori, an ascending trench cut into a slope, cut deep into the mountains. To the north, there was a samurai-machi, the residential district for samurai, in addition to the sea. To the east, there was a deep valley with a river at its bottom. The castle moat had rocks on its sides. These features made it an impregnable fortress. Shiki Rinsen, the last head of Shiki clan, was the first one to propagate Christianity in Amakusa and was the leader of the Amakusa Goninshu. However, he was attacked by the allied forces of Konishi Yukinaga and Kato Kiyomasa in 1589, and he fled to Izumi looking to the Shimazu clan in Satsuma for help. Only a few vestiges of the castle that existed in the past still remain today