Achasanseong

Lore & Background

The first historical mention of Achasanseong comes from the Samguk sagi, which records that King Chaekgye of Baekje ordered it fortified against an expected Goguryeo invasion. At that time, the fortress would have been crucial for defending the Baekje capital Hansŏng from the north.

In 475, Goguryeo overran this and other Baekje defenses, and King Gaero of Baekje was brought to Acha and executed. The fortress and the rest of the Han River valley were conquered by Silla in 553. The Goguryeo general On Dal later died here while trying to reclaim the fortress.

Achasanseong was designated as a historic landmark in 1973 and has since become a common local tourist destination.

Reader's Guide

Achasanseong is significant as a Three Kingdoms-era earthen fortress that changed hands among Baekje, Goguryeo, and Silla, reflecting the shifting power dynamics of the period. Its mention in the Samguk sagi ties it directly to the defense of the Baekje capital Hansŏng and the execution of King Gaero in 475. The fortress also marks the death of Goguryeo general On Dal during an attempt to reclaim it. Designated a historic landmark in 1973, Achasanseong now serves as a local tourist destination, offering visitors a tangible link to Korea's early medieval history. Its location at 200 meters above sea level on Mount Achasan provides a strategic vantage point, and its perimeter of roughly 1 kilometer and area of about 3375 m² illustrate the scale of such fortifications. The site's legacy lies in its role as a contested stronghold during the Three Kingdoms period and its preservation as a cultural heritage site.

Did You Know?

• Achasanseong was originally built by Baekje and later occupied by each of the Three Kingdoms.
• King Gaero of Baekje was brought to Acha and executed after Goguryeo overran the fortress in 475.
• The Goguryeo general On Dal died at Achasanseong while trying to reclaim it.
• The fortress was designated a historic landmark in 1973.