A key castle fought over by the Owari and Mikawa domains

When Iwasaki Castle was constructed is unknown, but it is said to have been built at the end of the Muromachi period. The Iwasaki area, where the castle lies, was the meeting point the Owari region in western Aichi and the Mikawa region in Eastern Aichi. The castle itself was held by Arakawa Yorimune, a vassal of Oda Nobuhide—the father of famous feudal unifier of Japan, Oda Nobunaga—but was taken by Matsudaira Kiyoyasu, the grandfather of yet another famous feudal unifier of Japan: Tokugawa Ieyasu. Later on, Niwa Ujikiyo of the Niwa clan moved to the castle from Hongo Castle in Nisshin City, and the clan remained there as lords for four generations. During the Battle of Komaki and Nagakute in 1584 between Toyotomi Hideyoshi and Tokugawa Ieyasu, the Niwa clan fought for the Tokugawa and was recognized for its allegiance, although they lost the castle in their attempt to halt the Hashiba forces' march from Inuyama to Okazaki.
In 1987, a five-story pseudo tower keep was built over the main precinct, and the castle premises were made into Iwasaki Castle Park. The park is also home to the Iwasaki Castle Historical Museum, with exhibits related to Iwasaki Castle as well as the chance to learn about Nisshin City's history and cultural heritages. Souvenirs are also available for purchase.