Believed to have been first built in 1566 by Toyotomi Hideyoshi, Sunomata-jō was established on the west bank of the Nagara-gawa, a strategic location for transport on one of the area's largest rivers. According to legend, the castle was built in one night - a myth referred to in the name of the current structure: Sunomata Ichiya-jō (墨俣一夜城). Abandoned after severe flooding in 1586 changed the course of the nearby Kiso-gawa, the site lay empty until a reconstruction was completed in 1992. The modern "replica" is in fact not an exact copy of the original, but rather one suiting the preference of local citizens (the old castle is not believed to have had a central donjon).