The castle is nicknamed 'Nabe-jo' (Pot Castle) because its low-lying position inside a valley makes it look like a pot when viewed from the outside.
It is one of the only Japanese castles that requires visitors to walk downhill to reach the center of the fortification.
The Sannomon Gate was reconstructed in the mid-Edo period after the original structure was destroyed by fire.
Author Shimazaki Tōson taught at a local school in Komoro, and his literature is deeply influenced by the atmosphere of the castle grounds.
The castle grounds were built using a base of volcanic rock from the nearby Mount Asama.
The park contains a memorial stone dedicated to haiku poet Takahama Kyoshi.
Kaikoen Park is a unique 'anajiro' (hole castle) situated in Komoro, Nagano, where the main castle grounds are located on lower ground than the surrounding town. The site preserves original stone walls and the Otemon Gate, dating back to the late 16th century construction under Sengoku-era daimyos. Its strategic design utilized the deep ravines of the Nunobiki Mountains to provide natural defenses. The park serves as a hub for the Tōson Memorial Museum, dedicated to the writer Shimazaki Tōson who lived in Komoro. Visitors can access preserved turrets like the Sannomon Gate, which is designated as an Important Cultural Property. The grounds are widely recognized as one of the premier locations in Japan for cherry blossom viewing. The park also hosts a small zoo and a botanical garden within its historic perimeter. It remains one of the few remaining examples of Japanese castle architecture that successfully integrated rugged natural topography into military fortifications.
The Sannomon Gate viewed from the main entrance approach.
Wear sturdy walking shoes to navigate the steep terrain and stone pathways.
Purchase a combination ticket to access both the historical sites and the internal museum exhibits.
Check the local bloom forecasts if visiting in spring, as peak dates vary annually.
Do not attempt to climb or sit on the historic stone walls, as they are fragile and pose a significant safety risk.
The park is generally open year-round, though specific museum buildings may close for short periods during the winter season.
Maintain silence near memorials and keep to the marked trails to protect the fragile stonework.
