According to Sinjungdonggukyojisungnam (Revised Handbook of Korean Geography) released in the 16th century and other historical books, the walls had been known to be built in the period of Koryo Kingdom (918-1392) at the initiative of a feudal bureaucrat, Kim Pu Sik, to quell the "revolt of Myo Chong".

After months of researches, those historians discovered the walls in Sonnae-dong (formerly called Sosan), Mangyongdae District, Pyongyang, and proved on a scientific basis that they date back to Koguryo Kingdom, not to Koryo Kingdom.

The walls cover a certain area southeast of the 92.6 meter-high hill, some 800 meters away from the place where the River Taedong joins the River Pothong and some 1 000 meters away from the River Pothong.

The rectangular walls are 2 170 meters long. The style of their construction and the shape of processed stones are the same as those used in Koguryo Kingdom.

Unearthed there were pieces of red-color tiles and earthenware and metal arrowheads, which are believed to be those of Koguryo Kingdom. Also discovered were pieces of tiles believed to be made in Koryo Kingdom, which suggested that the walls had been used in the period of Koryo Kingdom, too.

Those relics and historical data evidently show that the walls were subsidiary ones built miles ahead of the Walled City of Pyongyang to reliably defend this capital of Koguryo.