Location: The Niwa District of Owari Province. The castle stood on a plain with a base elevation of only ten meters. The dimensions were 104 meters from east to west and 169 meters from north to south. Otai castle was situated to the south of Iwakura.
History: Built around 1479 by Oda Toshihiro, a retainer of the Shiba clan and shugodai of the four northern districts in Owari. Iwakura served as an important base for the governance of the Ise-no-kami branch of the Oda clan. In 1556, while serving as lord of the castle, Oda Nobuyasu joined forces with Oda Nobuyuki in opposition to Nobunaga at the battle of Inō. In 1558, Oda Nobukata, the lineal successor of Nobuyasu, took refuge in Iwakura after losing against Nobunaga in the battle of Ukino. He surrendered the castle in 1559 following an attack by Nobunaga.