Odusanseong Fortress

Odusanseong Fortress is a Goguryeo-period mountain fortress in Paju, Gyeonggi-do, set on Mt. Odusan at a strategic point overlooking the Imjin River where it meets the Han River — a position of historical military importance for protecting the Goguryeo kingdom's southwestern frontier during the Three Kingdoms period. The fortress is one of Korea's older surviving fortress sites, with archaeological evidence pointing to original construction during the Goguryeo period (5th-7th centuries CE) and use through the subsequent Baekje and Silla contest for control of the Han River basin. Walking the fortress walls provides historical-and-archaeological insight along with broad open-sea-and-river views back across the Han River and Imjin River confluence — one of the few points where visitors can see North Korean territory across the water on clear days. The site is also located within the broader inner Korean border zone, near the DMZ, and visitors should confirm current access rules before travel as parts of the surrounding area fall inside the Civilian Control Line. Best paired with the Odusan Unification Observatory (also on Mt. Odusan) for a combined Goguryeo-fortress-and-modern-observation-deck visit, ideally on a clear autumn or spring day when the view across the water is sharpest.