Inuyama Castle Keep: Japan's Oldest National Treasure Castle Tower

Standing proudly atop a cliff overlooking the Kiso River in Aichi Prefecture, Inuyama Castle is one of the most treasured historical landmarks in Japan. Its keep—designated as a National Treasure—is among only five castle towers in the country to hold this prestigious distinction, alongside Himeji, Matsumoto, Hikone, and Matsue castles. With its origins dating back to 1537, Inuyama Castle's wooden tower is considered one of the oldest surviving keeps in Japan, offering visitors a rare and authentic glimpse into the architecture and spirit of the Sengoku (Warring States) period.

Known also by its poetic alias "Hakutei-jō" (White Emperor Castle)—a name inspired by the Chinese poet Li Bai's verse about a castle on the Yangtze River—Inuyama Castle captivates visitors with its dramatic hilltop setting, centuries-old wooden interiors, and sweeping panoramic views that stretch across the Nobi Plain to the distant peaks of Mount Ontake.

A Storied History: From Warring States to Modern Times

Inuyama Castle was originally constructed around 1537 by Oda Nobuyasu, the uncle of the legendary warlord Oda Nobunaga. Situated at the strategic border between the provinces of Owari (western Aichi) and Mino (southern Gifu), the castle occupied a vital military position controlling both the Kiso River crossing and the routes along the Nakasendo and Kiso highways.

Throughout the turbulent Sengoku period, the castle changed hands repeatedly among powerful warlords. After Oda Nobunaga's assassination at Honnō-ji in 1582, the castle became a flashpoint in the Battle of Komaki and Nagakute (1584), when Toyotomi Hideyoshi himself established his headquarters within its walls to confront Tokugawa Ieyasu. The fact that all three of Japan's great unifiers—Nobunaga, Hideyoshi, and Ieyasu—each controlled Inuyama Castle at different times speaks to its extraordinary strategic importance.

In 1617, the Naruse clan received the castle from the Owari branch of the Tokugawa family, and it remained under their stewardship for over 380 years. The Naruse lords carried out significant renovations, adding the distinctive karahafu (cusped gable) windows that define the keep's elegant silhouette today. Remarkably, Inuyama Castle was the last privately owned castle in Japan, remaining in the Naruse family's possession until 2004 when it was transferred to the Inuyama Castle Hakutei Library Foundation.

Why Inuyama Castle Keep Is a National Treasure

The keep of Inuyama Castle was first designated as a National Treasure in 1935 and received renewed designation under the Cultural Properties Protection Act in 1952. Several factors contribute to its extraordinary cultural and architectural value.

As one of only twelve original castle keeps surviving from the Edo period or earlier, and one of just five designated as National Treasures, Inuyama Castle's keep represents an irreplaceable testament to Japanese castle architecture. The tower's "bōrō-gata" (watchtower-style) construction—where a lookout tower sits atop a lower residential structure—is among the oldest examples of this architectural form in existence.

Research conducted during the major restoration of 1961–1965 revealed that the keep underwent several phases of construction. Recent dendrochronological studies (tree-ring dating) suggest the current three-story, four-level structure was built around 1590, though the Naruse clan's early 17th-century additions gave the tower its present refined appearance. The timber framework preserves traces of traditional hand-hewn construction techniques, including marks from large two-person saws (ōga) and adzes (chōna), offering tangible connections to the craftsmen of centuries past.

Architectural Highlights and Features

The keep stands approximately 24 meters tall, including a 5-meter stone foundation, and features three visible roof layers housing four above-ground stories and two basement levels. Visitors enter through the stone foundation on the south side, passing through the atmospheric basement levels before ascending to the main floors above.

The first floor is arranged around four central rooms encircled by a "musha-bashiri" (warrior's corridor), a passage designed to allow defenders to move quickly around the perimeter. The southwest chamber, known as the "jōdan-no-ma" (elevated room), features a raised tatami floor with a tokonoma alcove, decorative shelving, and a chōdai-gamae screen—elements of formal shoin-style architecture added during the early 19th century. Two stone-dropping chutes (ishi-otoshi) on the northwest and northeast corners reveal the keep's military origins, designed to repel attackers scaling the walls below.

The second floor served as the armory (bugu-no-ma), where weapons were stored centrally for rapid deployment. The third floor, concealed within the roof structure, comprises a pair of compact rooms known as the "hidden level." The crowning glory awaits at the fourth floor, where an open-air balcony (mawari-en) encircles the entire tower. From this vantage point, visitors enjoy an unobstructed 360-degree panorama encompassing the Kiso River, the Nobi Plain, Gifu Castle, and on clear days, the snow-capped peak of Mount Ontake.

The "Rear-Fortified Castle": Strategic Design

Inuyama Castle is a classic example of a "ushiro-kengo no shiro" (rear-fortified castle). Built atop a hill approximately 85 meters above sea level on the south bank of the Kiso River, the castle's rear faces a sheer cliff dropping straight down to the river, making any attack from the north virtually impossible. The river served as a natural moat of formidable proportions.

From the main bailey (honmaru) at the summit, a series of secondary enclosures—Sugi-no-maru, Momi-no-maru, Kiri-no-maru, and Matsu-no-maru—cascade down the southern slope like a grand staircase. The castle's "sōgamae" (comprehensive fortification) design originally incorporated the entire castle town within its defensive perimeter, surrounding both the fortress and the civilian settlement with moats and earthworks.

The Poetic Name "Hakutei-jō" (White Emperor Castle)

The castle's elegant alternate name, Hakutei-jō, was bestowed by the renowned Edo-period Confucian scholar Ogyū Sorai. Gazing upon Inuyama Castle rising above the Kiso River, Sorai was reminded of Baidi Cheng (White Emperor City) along the Yangtze River in China, immortalized in the Tang dynasty poet Li Bai's famous verse "Departing Early from Baidi City." This literary association lends Inuyama Castle an aura of classical refinement that extends beyond its military heritage, connecting it to a broader tradition of East Asian landscape appreciation.

Visiting Inuyama Castle: What to Expect

A visit to Inuyama Castle is an immersive journey through Japanese history. The approach along the original ōte-michi (main castle road) winds uphill through stone walls and ancient trees, building anticipation before the keep reveals itself against the sky. Inside the tower, the steep, narrow wooden staircases are part of the authentic experience—wear comfortable shoes and be prepared for a climb that rewards you with one of the finest castle-top views in all of Japan.

The castle is open from 9:00 to 17:00 (last entry at 16:30) year-round, except December 29–31. To avoid crowds, arrive early in the morning or after 15:00, especially on weekends and holidays when entry may be restricted due to the keep's limited capacity. Audio guides and multilingual information are available to help international visitors appreciate the castle's rich history.

Nearby, the Sanko Inari Shrine with its photogenic rows of vermilion torii gates and heart-shaped ema (votive tablets) sits at the foot of the castle hill, while the Haritsuna Shrine hosts the spectacular Inuyama Festival each spring, featuring elaborate mechanical puppet floats (karakuri yama) that are themselves designated as an Important Intangible Folk Cultural Property.

Inuyama Castle Town: Edo-Period Charm Preserved

Extending south from the castle, the Inuyama Castle Town retains the original street layout established during the Edo period. Historic machiya townhouses and traditional shops line the avenues, now enlivened with cafés, craft stores, and local delicacies. The area escaped wartime destruction, preserving an atmosphere that transports visitors back in time.

Popular local treats include gohei-mochi (pounded rice cakes with walnut miso glaze), dengaku (grilled tofu with hatcho miso), and colorful dango (rice dumplings). Visitors can also rent kimono for a leisurely stroll through the streets, creating memorable photographs against the backdrop of preserved Edo-era architecture.

Within walking distance, the Japanese Garden Uraku-en houses the National Treasure tea room "Jo-an," built by Oda Uraku (brother of Oda Nobunaga) and one of the finest examples of tea ceremony architecture in Japan. A combined ticket for both Inuyama Castle and Uraku-en allows visitors to experience two National Treasures in a single visit.

Surrounding Attractions

The Inuyama area offers a wealth of additional cultural and recreational experiences. The Museum Meiji-mura, located about 20 minutes by car, is an open-air architectural museum preserving over 60 buildings from the Meiji era (1868–1912), including the entrance hall of Frank Lloyd Wright's Imperial Hotel. Little World, a museum of world cultures, and the Japan Monkey Centre, home to the world's largest collection of primate species, are also nearby.

For those seeking relaxation, the Inuyama Onsen hot spring area along the Kiso River provides traditional Japanese ryokan accommodations with views of the castle and river. The Kiso River itself offers seasonal cormorant fishing (ukai) viewing from June to October, a tradition dating back over 1,300 years.