Komoro Castle is known as a "Sunken Castle" because it was built on natural terrain below the surrounding town level, making it architecturally rare among Japanese castles. While most castles are constructed on elevated positions for defensive purposes, Komoro Castle's unique topography creates an unusual sunken appearance. The castle also retains its original San-no-mon (third gate), which is designated as a Nationally-Designated Important Cultural Property.
The park is recognized as one of Japan's top 100 cherry blossom spots. Due to Nagano's cooler climate, the cherry blossoms bloom later than in other regions, typically lasting until late April. This extended blooming period makes it an excellent destination for visitors who may have missed the earlier sakura season elsewhere in Japan.
The castle ruins are easily accessible with just a 3-minute walk from Komoro Station. From Karuizawa, take the Shinano Line for 24 minutes. From Nagano, the journey takes approximately 60 minutes on the same line. Komoro city is located about 20 km west of Karuizawa in Nagano Prefecture.
While the original castle keep no longer exists, visitors can explore the labyrinthian stone walls, several original castle gates, and moss-covered stone foundations. The park also houses museums with art and historical artifacts from Komoro's history. The site functions as a beautiful municipal park where you can experience the seasonal beauty of cherry blossoms, autumn colors, and diverse flora throughout the year.
The basic entrance fee to Kaikoen Park is ¥200. For a more comprehensive experience, a combined ticket is available for ¥500 that includes access to the on-site museums housing art and various artifacts from Komoro's history. The park offers good value as it's listed among Japan's Best 100 Castles, Best 100 Sites for Cherry Blossom Viewing, and Best 100 Historical Parks.
Traveler reviews
Its park is worth visiting and is highly accessible. If you want to take photos of autumn leaves, this is a recommended place.
This is 2nd time we are here, the flower not yet bloomed yet. Beautiful and lovely place which I really enjoyed
Kaikoen(castle ruins), Komoro, Nagano, Japan. The Yatsugatake High Country rail which passes the highest station in the whole of Japan: Nobeyama is a restful way to see the spectacular countryside of the Japan alps on the way to the the castle ruin park Kaikoen of Komoro in Nagano Japan.
400 yen includes tickets to the Memorial Hall of Toson, the Koyama Keizo Museum of Art, and the Chokokan weapons museum. The castle ruin gardens are free. Toson was one the major authors of the Meiji period renowned for social realism; ‘The Broken Commandment’ depicts the life of a young man born into the despised burakumin class. Keizo Koyama’s Japanese western style paintings recapture the beauty of Komoro and the surrounding alps. Bridges, stone gardens and all that Japanese traditional gardens encapsulate can be found in this peaceful, uncrowded castle ruin park. Come November, the autumnal reds will bring the park ablaze, just as spring with transform the park with the cherry blossoms.
Opposite the park’s entrance a long line of people wait patiently for a seat in Kusabue (Whistling Grass) Soba restaurant . Be sure to write your name in the book before lining up!!! We lined up for maybe 30 minutes and we’re not disappointed; Toson soba included tempura, apples, walnuts, wakame(seaweed) and nagaimo(mountain potato).
The station is filled with home grown produce and an honesty box. We feasted on fresh apples on our train trip home. Four apples for 200 yen.
Komoro is well connected by rail and well off the usual tourist track.
Nice park to visit while in Komoro. The zoo is getting a renovation and the new penguin enclosure looks pretty nice and decent. The entrance fee to the park is affordable at 500 yen for a combined ticket to visit some of the museums which houses art and various artifacts from Komoro's history. Worth a visit for those who want a quiet place without much tourist and an insight into some of the town's history and sights.
I visited Kaikoen Park in September 2025. It was from Saitama where it was super hot. I was able to enjoy the cooler temperature in Kaikoen.
The inside was so huge that it took an hour or more to walk around the park. I had to take the next train on the Koumi line, where there are a few trains. I should be in a hurry.
I heard that someone said" Shimazaki Fujimura Memorial Museum". I think it should be Touson instead of Fujimura. LOL.
I guess that sakura flowers will be blooming in April. I wish I could visit Kaikoeen in Spring.
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