The walls, believed to be built with earth in 1107 in an aim to defend the northern territory, were repaired in 1437.

Rebuilt in 1616-1622, they are 810 meters long from east to west and 290 meters long from north to south.

The walls, nine meters high, eight meters wide in the lower part and three to four meters wide in the upper part, have four gates in the north, south, east and west.

With 510 battlements, there is a 34-meter-wide and 4.5-meter-deep moat outside the walls.

Unearthed in the walled township were sites of storehouses, armories, 12 ponds and 54 wells.

Listed as one of national heritages, the walls give a glimpse of the architectural art of the Korean people in the middle ages.