Koguryo moved its capital to Pyongyang in the year of 427 and built the walls in the latter half of the 6th century (552-586). Six wall stones inscribed with letters were found in modern ages, which proved the stage, period and scale of the wall construction.

The Walled City of Pyongyang with about 16 kilometers in circumference of the walls, 23 kilometers in total length of the walls and 11.85 square kilometers in total area has Moran Hill in the north and Taedong and Pothong Rivers in the east, west and south, which provided natural and geographical conditions unfavorable for the foreign invaders and favorable for defenders.

It, which was called Jangan Walls, consisted of four castles -- Naesong (inner castle) where the royal palace was located, Jungsong (middle castle), the administration centre of Koguryo, where central government offices were located, Woesong (outer castle) where there were main residential quarters and Puksong around Moran Hill (outer ring walls for defending the city). According to a historical record, there were more than 210,500 households inside and outside of the walls.

The walls were 4-5 meters high in hilly lands and 7-9 meters high in flat areas. The Walled City Pyongyang was really an impregnable fortress with various defence facilities, many wall gates and commanding posts in the walls.

The Taedong Gate, Pothong Gate, Chilsong Gate, Ulmil Pavilion, Ryongwang Pavilion, Pubyok Pavilion, the sites of Naesong and Woesong and other relics of the Walled City of Pyongyang which are preserved as they were are valuable cultural legacies showing the might and development of Koguryo.