Exploring Komoro Castle, One of Japan’s Top 100 Historic Castles

Source: Japan National Tourism Organization

Komoro Castle is one of Japan’s Top 100 Castles and one of the country’s most unusual castle sites. Built in a region shaped by volcanic activity and deep valleys, the castle relied heavily on its natural surroundings for defence. Today, the site is preserved as Kaikoen Park, where visitors can explore historic ruins while enjoying seasonal scenery such as cherry blossoms in spring and vibrant foliage in autumn.

Unlike most Japanese castles that sit on hilltops, Komoro Castle was built at a lower elevation, with its key structures positioned beneath the surrounding terrain. That is how it came to be known as a “pit castle.”

Nearby stands Mount Asama, an active volcano rising to around 2,500 metres. Over time, volcanic activity created deep valleys throughout the region, naturally shaping the land into a defensive stronghold. Below the castle flows the Chikuma River, which later becomes the Shinano River, the longest river in Japan.

With steep terrain, riverbanks, and volcanic landforms acting as barriers, Komoro Castle relied less on tall walls and more on its environment for protection. It is a rare example of a castle where nature itself played the leading defensive role.

Today, the former castle grounds are preserved as Kaikoen Park, a historic public park that is enjoyed throughout the year. In spring, the park attracts many visitors for cherry blossom viewing, with rows of sakura trees set against the remains of the castle and the surrounding valley. In autumn, the area transforms again, drawing visitors with vibrant red and gold foliage.

Source: Nagano Prefecture & Nagano Tourism Organization

One of the highlights of Kaikoen Park is the viewpoint, where the landscape opens up all at once. From here, visitors can take in sweeping views of the natural features that once protected the castle.

Source: NAVITIME JAPAN

Inside the park, there is also a small zoo and an amusement area, making it a popular destination for families, especially during spring and autumn.

Throughout the year, Kaikoen Park hosts seasonal events and festivals that coincide with the changing seasons. These events add activity to the historic grounds and give visitors a reason to return at different times of the year.

Just outside the park, visitors will also find the main branch of Kusabue, one of Nagano’s most famous soba noodle restaurants. After exploring the castle grounds, enjoying a bowl of freshly made soba is a fitting way to end the visit.

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