Namhan Sanseong is a historic mountain fortress located in South Korea, built during the late 17th century. It was constructed to protect the capital, Seoul, from invasions, particularly during the Korean conflicts with the Manchu and Japanese forces. The fortress features impressive stone walls, watchtowers, and various gates, showcasing traditional Korean military architecture. Today, Namhan Sanseong is a popular tourist destination and a UNESCO World Heritage site. Visitors can explore its scenic hiking trails, enjoy panoramic views of the surrounding landscape, and learn about its historical significance through various exhibits and guided tours.