Excavations at Jangmisan Fortress in Chungju, North Chungcheong Province, have uncovered the largest Baekje water storage facility from the Hanseong Period (from the foundation until the capital moved to Ungjin in 475) ever found, along with elite fortress-building techniques typically reserved for royal capitals.

On December 1, the National Research Institute of Cultural Heritage under the Korea Heritage Service announced the excavation results, highlighting the discovery of a large wooden water reservoir (jipsuji) and rammed-earth (panchuk) fortress walls.

The reservoir, unearthed in the northern valley within the fortress, features a square layout measuring roughly 6.7 meters per side internally and 1.8 meters in depth. It stands as the oldest and largest wooden water reservoir from the Baekje period discovered so far. Constructed by interlocking logs over 7 meters long across nine tiers, it has a maximum capacity of about 80,000 liters—enough water to support 300 people for roughly two and a half months. A smaller, well-style catchment facility was also found just south of it, suggesting that drinking water and utility water were managed separately.

Beneath the existing stone walls, researchers also identified Hanseong-period rammed-earth walls. Rammed-earth construction involves building square frames and compacting alternating layers of soil with different physical properties. Because this technique requires elite central engineers, massive labor, and substantial resources, it was typically restricted to royal capitals or vital regional hubs. Kwon O-young, a professor of Korean history at Seoul National University, noted that such engineering reflects direct mobilization by the central government. A large quantity of central-style Baekje pottery and lacquerware was also unearthed at the site.

The soil accumulated inside the reservoir yielded over 50 plant species, including rice, soybeans, red beans, and burdock, alongside animal bones from cattle, horses, pigs, and dogs. At the bottom of the reservoir, the intact skeletons of a newborn pig and a dog were found alongside deliberately damaged pottery, pointing toward ancient ritual activities.

Furthermore, the site yielded straw baskets (samtaegi) and cow nose rings (sokoture) analyzed to be the oldest ever identified in South Korea, as well as the nation's first fully intact iron axe featuring an attached wooden handle. The research institute stated that these artifacts provide vital data for reconstructing the daily lives and surrounding environment of the people at Jangmisan Fortress in the 5th century.

Chungju served as a vital transportation hub connecting to the Baekje capital of Hanseong via the upper Han River and linking to the inland Yeongnam region through mountain passes like Gyeryipryong and Joryung. Lee Bo-ram, a researcher at the institute, evaluated that Jangmisan Fortress operated far beyond a simple defensive fortification, functioning as a key strategic foothold in the Jungwon region backed by the central government's technology, manpower, and resources.

A special exhibition showcasing these excavated artifacts is running at the exhibition hall of the National Research Institute of Cultural Heritage until December 31.