Built in: 1571 by Baba Harunobu.
Koyama Castle was constructed in 1571 by Baba Harunobu. Takeda Clan constructed this castle to attack Takatenjin castle of Tokugawa Ieyasu. In 1582, when Tokugawa Ieyasu and Oda Nobunaga attacked Takeda clan and the land of Kai, this castle was defeated and abandoned.
It has all kinds of the features of Takeda Style castle. Especially, 3 layered Crescent moats are the unique feature to this castle. Legend said, when this castle was follen, all the women jumped into the moat, and ever since then, red leeches started living this moat.