Namhansanseong is a historical mountain fortress city 25 km southeast of Seoul, South Korea. It sits approximately 480 m above sea level and is aligned with the ridges of the mountain for maximum defensibility. The fortress, stretching 12 km in length, protects a vast area used as an emergency capital city during the Joseon Dynasty of Korea (1392–1910). The design is based on fortress architecture of East Asia, embodying aspects of four historical cultural styles: the Joseon of Korea, the Azuchi-Momoyama Period of Japan, and Ming and Qing China. It was extensively developed during the 16th to 18th centuries, a period of continuous warfare. The technical development of weaponry and armaments during this period, which saw the use of gunpowder imported from Europe, also greatly influenced the architecture and layout of the fortress. Namhansanseong portrays how the various theories of defense mechanisms in Korea were put to form by combining the everyday living environment with defense objectives. The fortress indicates how Buddhism played an influential role in protecting the state, and it became a symbol of sovereignty in Korea. It stands on the Namhansan (South Han Mountain), containing fortifications that date back to the 17th century and a number of temples. It can be accessed from Seoul through Namhansanseong station of Seoul Subway Line 8. History The most obvious characteristic of Namhansanseong lies in its topographical advantage; there is a spacious, flat top called Gorobong, with a low center and high sides over 480 m above sea level, as well as being a high mountain over flat lands for easy observation of the surrounding area. Due to these traits, Namhansanseong had served as a command post since the Unified Silla era in the 7th century. Unified Silla constructed the Jujangseong fortress where Namhansanseong sits today to house men and to stock supplies when it was fighting the Tang dynasty in the 7th century. In the 13th century, during the Goryeo dynasty, Namhansanseong was a stronghold against the Mongol Invasion. Since the 17th century, Namhansanseong, near the capital city of Seoul, grew greatly in size as a mountain fortress, serving as an emergency capital for the King of Joseon. Furthermore, Namhansanseong had been systematically managed and operated for over 300 years since its construction in 1624. Specifically, it was a battlefield during the Qing invasion to acquire hegemony in East Asia during the Ming-Qing transition in China. It was the spiritual