Tsumago Castle (御城印 - Goshu-in, a castle stamp) This was an important mountain castle from the Warring States period, located in Nagiso Town, Nagano Prefecture. It guarded a strategic point at the confluence of the Nakasendo and Otaira Kaido roads and was built in the mid-Muromachi period. In particular, during the 1584 "Battle of Komaki and Nagakute," it is known as an impregnable fortress where the Toyotomi forces, defended by Yoshimasa Kiso, repelled a large Tokugawa army. Currently, remnants such as earthen walls and horikiri (dry moats) remain.