Pyongyang, August 24 (KCNA) -- The Kaesong Walls and the Kaesong Nam Gate in Kaesong City, the DPRK, were listed as the world's cultural heritages in late June. The Kaesong Walls extending 23 kilometers surround Kaesong City, the capital of Koryo (918-1392), Korea's first unified state. The walls consist of royal fort, divided into Hwang and Kung forts, and inner and outer forts. Hwang Fort was built with Kung Fort along the foot of Mt. Songak in 896, early period of building Koryo. The Outer Fort, 16 km long, was built against the invasion of outsiders in 1029 with mobilization of more than 230 000 laborers and 8 450 technicians, according to "Koryo History", an ancient document. The Inner Fort, 8.5 km long, was built in 1391-1393. The Kaesong Nam Gate is the south gate to the Inner Fort in the Kaesong Walls. It was built late in the period of Koryo Kingdom. The gate consists of the gateway structure built with well-trimmed rectangular plane granite stones and a pavilion above it. The hip-saddle roof pavilion with double eaves is 13.63 meters long on the front and 7.96 meters wide on the flank. Yonbok Temple Bell, one of the three famous bells in the DPRK, is in the pavilion.