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Sam Nyeon San Seong Fortress - 삼년산성 (三年山城) (from 5th century onward)

At the crest of Mt. Ojeongsan east of Boeun-eup stands Sam Nyeon San Seong, the remains of a powerful fortress from the late 5th century. Now partially reconstructed, the fortresss commands a fine view of the nearby plains. According to the Samguksagi (Historical Record of the Three Kingdoms), it was built in 470 (the 13th year of King Jabi's reign) and was rebuilt in 486 (the 8th year of King Soji's reign) during the Silla dynasty. The book also says that it was named Sam Nyeon San Seong ('Sam Nyeon' means 'three years') because it took three years to complete the fortress wall. The Boeun area was called Samnyeonsan-gun in 553 during the reign of King Jijeung and then was renamed Samnyeon-gun in 742 during the reign of King Gyeongdeok. Judging from this fact, we can infer that Sam Nyeon San Seong was important enough that it gave its name to the area.

During the unification wars of the late 7th century, the fortress occupied a pivitol position in the conflict. Sam Nyeon San Seong was an important forward base that allowed Silla to hold the line against Baekjae to the west while allowing its own troops to advance northward into the Sangju area in preparation for a Goguryeo attack from the north. Thanks to this fortress wall, Silla was able to conquer the Hangang basin when the three kingdoms were in a state of war.

The fortress is also sometimes known as Ojeongsanseong (Ojeongsanseong Fortress Wall) because it is located on Mt. Ojeongsan. The fortress sits like a folding screen along the mountain ridge, running in a 1.88 kilometer loop that encloses a fair amount of land. It is said that inside the walls there was once a large pond that provided drinking water for the defenders, but the pond is now largely dry and only its outline can be seen. The fortress once boasted four gate sites, 7 curved bastions, and two sluice gates, but most of these have crumbled to ruin over the years. The current reconstruction is slowly restoring parts of the loop, but the use of modern cut stone makes the reconstructed areas stand out from the original ruins.

At the current entrance to the fortress one can examine a boulder face carved with calligraphy. This is believed to be the work of Kim Saeng, but there is no definite date.

Address: 충북 보은군 보은읍 어암리 산1-1.

(Designated Historical Site #235).