the defense system, were first established in 1394 and remained in operation until 1894. Signals sent across the country from one mound to another, using smoke by day and fire at night, were received by the beacon at the top of Namsan and conveyed to the Royal Palace. Gates Four main gates and four auxiliary gates were built around Seoul in the late 14th century. The four main gates were Heunginjimun (East Gate), Donuimun (West Gate), Sungnyemun (South Gate), and Sukjeongmun (North Gate). The four auxiliary gates were placed in areas between the four main gates, with Souimun (in the southwest), Changuimun (in the northwest), Hyehwamun (in the northeast), and Gwanghuimun (in the southeast). At present, the following gates are either preserved in their original form or have undergone restoration work: Sungnyemun (South Gate) and Heunginjimun (East Gate) are designated as National Treasure No. 1 and Treasure No. 1, respectively. Condition Hanyangdoseong, completed in 30 years, was torn down in many parts due to city planning initiatives and the introduction of trams lines. However, significant sections of the wall remain. The best-preserved and well-known course is the Wall of Mt. Bukaksan, the 2.3-km trail which cuts through Sukjeongmun to Changuimun. Previously off-limits to the public after having been designated as a Military Reserve area due to its close proximity to Cheongwadae, it opened to the public in 2006. With very few alterations or artificial structures surrounding the area over the years, the natural environment remains relatively intact. Trail tour The city of Seoul operates the Hanyangdoseong stamp trail tour, which runs along the wall, divided into six trails: Baegak Mountain Trail Naksan Mountain Trail Heunginjimun Gate Trail Namsan(Mongmyeoksan) Mountain Trail Sungnyemun Gate Trail Inwangsan Mountain Trail Gallery See also The Eight Gates of Seoul Notes References Korean Exploring Online Fortress Wall of Seoul Korean Britannica Online Buildings and structures completed in 1396 History of Seoul Buildings and structures in Seoul Tourist attractions in Seoul Castles in South Korea Seoul Historic Sites of South Korea World Heritage Tentative List