<P> Seoul has been surrounded by walls that were built to regulate visitors from other regions and protect the city in case of an invasion . Pungnap Toseong is a flat earthen wall built at the edge of the Han River, which is widely believed to be the site of Wiryeseong . Mongchon Toseong (Hangul: 몽촌 토성; Hanja: 蒙 村 土 城) is another earthen wall built during the Baekje period that is now located inside the Olympic Park . The Fortress Wall of Seoul was built early in the Joseon Dynasty for protection of the city . After many centuries of destruction and rebuilding, approximately 2⁄3 of the wall remains, as well as six of the original eight gates . These gates include Sungnyemun and Heunginjimun, commonly known as Namdaemun (South Great Gate) and Dongdaemun (East Great Gate). Namdaemun was the oldest wooden gate until a 2008 arson attack, and was re-opened after complete restoration in 2013 . Situated near the gates are the traditional markets and largest shopping center, Namdaemun Market and Dongdaemun Market . </P> <P> There are also many buildings constructed with international styles in the late 19th and early 20th centuries . The Independence Gate was built in 1897 to inspire an independent spirit . Seoul Station was opened in 1900 as Gyeongseong Station . </P> <P> Various high - rise office buildings and residential buildings, like the Gangnam Finance Center, the Tower Palace, Namsan Seoul Tower, and the Lotte World Tower, dominate the city's skyline . The tallest building is Lotte World Tower, reaching a height of 555m . It opened to the public in April 2017 . </P> <P> The World Trade Center Seoul, located in Gangnam District, hosts various expositions and conferences . Also in Gangnam District is the COEX Mall, a large indoor shopping and entertainment complex . Downstream from Gangnam District is Yeouido, an island that is home to the National Assembly, major broadcasting studios, and a number of large office buildings, as well as the Korea Finance Building and the Yoido Full Gospel Church . The Olympic Stadium, Olympic Park, and Lotte World are located in Songpa District, on the south side of the Han River, upstream from Gangnam District . Three new modern landmarks of Seoul are Dongdaemun Design Plaza & Park, designed by Zaha Hadid, the new wave - shaped Seoul City Hall, by Yoo Kerl of iArc, and the Lotte World Tower, the 5th tallest building in the world designed by Kohn Pederson Fox . </P>

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