Doksanseong Fortress and Semadae

A ring of walls encircles the top of Doksan, a low hill in Jigot-dong, Osan. This is Doksanseong, the fortress General Gwon Yul held with 20,000 troops during the Japanese invasions of the 1590s. Its great weakness was a lack of water, and the legend of Semadae (洗馬臺), the 'terrace where the horse was washed', tells how Gwon Yul fooled the enemy by pretending to wash his horse with white rice. The story has become almost a second name for the hill.

From Baekje to King Jeongjo

No one knows exactly when Doksanseong was first built, but it is thought to be a Baekje fortress. It remained strategically important in the Unified Silla and Goryeo periods; its older names were Seokdaesan and Hyangnobong, and in the Joseon era it was called Doksanseong.

Its most dramatic moment came during the Imjin War, the Japanese invasions of 1592–1598. Gwon Yul marched up from Jeolla Province with some 20,000 men, made camp here and blocked the advance of a Japanese army led by Ukita Hideie. Sources date his stand to December 1592 or to 1593. Local people rebuilt the walls in 1594, in 1602 the provincial defence commander Byeon Eung-seong rebuilt them in stone, and further work was done in 1792 and 1796 under King Jeongjo, around the time the nearby Hwaseong Fortress in Suwon was being built.

The legend of Semadae

Realising the fortress was short of water, the Japanese surrounded it and waited for the defenders to run dry. Gwon Yul then led a white horse to a prominent spot on the summit and poured white rice over it as if he were washing it. From a distance the rice looked like water, so the Japanese concluded that there was enough water up there to wash horses and withdrew. That is why the high terrace is called Semadae, and why nearby Sema Station on Line 1 bears the same name.

What to see

• Wall walk: The main wall is about 1,100 m around, with an inner wall of 350 m. Walking the circuit gives wide views over Osan, Dongtan and the surrounding farmland. Four gates and sections of wall survive.
• Semadae Pavilion: The pavilion on the summit was rebuilt in 1957 and carries a 'Semadae' signboard in the handwriting of President Syngman Rhee.
• Bojeoksa: A small temple just inside the east gate, said to have been founded in 401 under King Asin of Baekje. Its name, 'temple of accumulated treasure', comes from a story about a poor old couple who offered their last measures of rice to the Buddha and came home to find their storehouse full.
• Byeon Eung-seong's stele: A granite stele honouring the man who rebuilt the walls in stone; it was moved to its present spot in 2021, when the west-gate car park was redeveloped.

Tripto tips

• Visiting: Open at all times, free of charge, with parking.
• Time needed: Climbing from the car park to Semadae and walking the circuit takes 1–2 hours.
• Best time: The wall walk is a well-known spot for sunrise and night photography, and sunset from Semadae over the fields to the west is lovely. The Doksanseong Culture and Arts Festival takes place every September.
• Walking route: Section 7 of the Samnam-gil, one of the Gyeonggi Old Roads, is the 8.2 km, two-hour Doksanseong-gil, linking Semagyo Bridge, Bojeoksa, Dolmen Park and Eunbit Stream Park. The pavement is narrow for the first 200 m or so near Semagyo, so watch for traffic.
• Getting there: The fortress is about 2 km west of Sema Station on Line 1. By car, use the car park by the west gate.
• Combine with: Yunggeolleung, the royal tombs of Crown Prince Sado and King Jeongjo, and Yongjusa Temple are around 10 minutes away by car.