Guide
Otani Castle Ruins is a historic mountain castle located on Mt. Otani (elevation 495.1m) in Nagahama City, Shiga Prefecture. It is celebrated as one of Japan's three great medieval mountain castles and served as the seat of power for the Azai clan for three generations during the Sengoku (Warring States) period. Today, it is designated as a National Historic Site, showcasing a complex defensive structure that utilizes the natural terrain. From the summit, visitors can enjoy a breathtaking panoramic view of Lake Biwa and the northern Lake Biwa region.
The history of Otani Castle dates back to its construction around 1525. The Azai clan used this stronghold to navigate the intense political landscape of the era, often clashing with powerful figures like Oda Nobunaga. The site is deeply intertwined with the tragic and romantic-era stories of Azai Nagamasa, Lady Oichi, and the three daughters of the Azai clan (Chacha, Hatsume, and Go). Following the fall of the castle, the area was later controlled by Hashiba (Toyotomi) Hideyoshi, who eventually built Nagahama Castle nearby, leading to the abandonment of Otani Castle. The site was officially designated as a National Historic Site in 1937.
The castle ruins feature a sophisticated layout where various enclosures (kuruwa) are strategically placed along the east and west ridges to utilize the natural topography. Key features to look for include the Honmaru (main enclosure), the site of the Great Hall, and the Ozuku (large gate/fortification) area, where well-preserved earthworks and stone foundations can be seen. The embankments near the summit (495m) demonstrate advanced medieval fortification techniques. Additionally, the Kiyomizu-dani area contains the remains of the residences where the Azai clan and their retainers once lived, providing a deeper understanding of medieval life.
As this is an open historical site, there are no official opening hours or entrance gates. The ruins are generally accessible throughout the day. While the structures are visible in any season, we highly recommend visiting during daylight hours for safety and visibility. For the best experience of the landscape and the surrounding views, a clear, sunny day is ideal.
Visitors can experience the physical layout of a Sengoku-era fortress by walking through the actual terrain. By following the paths of the earthworks, embankments, and stone walls, you can trace the defensive strategies used by the samurai of the past. The hike offers a unique way to learn about mountain castle architecture while enjoying the expansive views of Lake Biwa from the top.
At the foot of Mt. Otani, you can find the Sengoku Guide Station and remnants of old checkpoints (Banjo). The surrounding area is dotted with various historical-related facilities and scenic spots around Lake Biwa. While rental cycles are available from Kamo Station, please note that the forest roads leading up to Mt. Otani are very steep and dangerous; cycling up the mountain is not recommended.
Because the site is a mountain castle, the terrain is unpaved, uneven, and often steep. Proper preparation is essential for safety.