The city has been known in the past by the names Wiryeseong (Hangul: 위례성; Hanja: 慰禮城, during the Baekje era), Hanyang (Hangul: 한양; Hanja: 漢陽, during the Goryeo era), Hanseong (Hangul: 한성; Hanja: 漢城, during the Joseon era), Keijō (Hangul: 경성; Hanja: 京城, during the colonial era).
During Japan's annexation of Korea, "Hanseong" (漢城) was renamed to "Keijō" (京城) by the Imperial authorities to prevent confusion with the hanja '漢' (a transliteration of an ancient Korean word "Han" (한) meaning "China"), which refers to Han people or the Han dynasty and in Japanese is a term for "China".
Its current name originated from the Korean word meaning "capital city", which is believed to be derived from the word Seorabeol (Hangul: 서라벌; Hanja: 徐羅伐), which originally referred to Gyeongju, the capital of Silla.
Unlike most place names in Korea, "Seoul" has no corresponding hanja (Chinese characters used in the Korean language). On January 18, 2005, the Seoul government arbitrarily changed its official Chinese name from the historic Hancheng (simplified Chinese: 汉城; traditional Chinese: 漢城; pinyin: Hànchéng), which had not fallen out of common use, to Shou'er (simplified Chinese: 首尔; traditional Chinese: 首爾; pinyin: Shǒu'ěr).
Seoul is in the northwest of South Korea. Seoul proper comprises 605.25 km2 (233.69 sq mi), with a radius of approximately 15 km (9 mi), roughly bisected into northern and southern halves by the Han River. The Han River and its surrounding area played an important role in Korean history. The Three Kingdoms of Korea strove to take control of this land, where the river was used as a trade route to China (via the Yellow Sea). The river is no longer actively used for navigation, because its estuary is located at the borders of the two Koreas, with civilian entry barred. Historically, the city was during the Joseon dynasty bounded by the Seoul Fortress Wall, which stretched between the four main mountains in central Seoul: Namsan, Naksan, Bukaksan and Inwangsan. The city is bordered by eight mountains, as well as the more level lands of the Han River plain and western areas. Due to its geography and to economic development policies, Seoul is a very polycentric city. The area that was the old capital in the Joseon dynasty, and mostly comprises Jongno District and Jung District, constitutes the historical and political center of the city. However, for example, the city's financial capital is widely considered to be in Yeouido, while its economic capital is Gangnam District.
Seoul is the business and financial hub of South Korea. Although it accounts for only 0.6 percent of the nation's land area, 48.3 percent of South Korea's bank deposits were held in Seoul in 2003, and the city generated 23 percent of the country's GDP overall in 2012. In 2008 the Worldwide Centers of Commerce Index ranked Seoul No.9. The Global Financial Centres Index in 2015 listed Seoul as the 6th financially most competitive city in the world. The Economist Intelligence Unit ranked Seoul 15th in the list of "Overall 2025 City Competitiveness" regarding future competitiveness of cities.
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.
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.
In 2010 Seoul was designated the World Design Capital for the year.
There are also many parks along the Han River, such as Ichon Hangang Park, Yeouido Hangang Park, Mangwon Hangang Park, Nanji Hangang Park, Banpo Hangang Park, Ttukseom Hangang Park and Jamsil Hangang Park. The Seoul National Capital Area also contains a green belt aimed at preventing the city from sprawling out into neighboring Gyeonggi Province. These areas are frequently sought after by people looking to escape from urban life on weekends and during vacations. There are also various parks under construction or in project, such as the Gyeongui Line Forest Trail, Seoul Station 7017, Seosomun Memorial Park and Yongsan Park.
Seoul is also home to the world's largest indoor amusement park, Lotte World. Other recreation centers include the former Olympic and World Cup stadiums and the City Hall public lawn.
Seoul has a comprehensive urban railway network of 21 rapid transit, light metro and commuter lines that interconnects every district of the city and the surrounding areas of Incheon, Gyeonggi province, western Gangwon province, and northern Chungnam province. With more than 8 million passengers per day, the subway has one of the busiest subway systems in the world and the largest in the world, with a total track length of 940 km. In addition, in order to cope with the various modes of transport, Seoul's metropolitan government employs several mathematicians to coordinate the subway, bus, and traffic schedules into one timetable. The various lines are run by Korail, Seoul Metro, Seoul Metropolitan Rapid Transit Corporation, NeoTrans Co. Ltd., AREX, and Seoul Metro Line 9 Corporation.
Compulsory education lasts from grade 1-9 (six years of elementary school and 3 years of middle school). Students spend six years in elementary school, three years in middle school, and three years in high school. Secondary schools generally require students wear uniforms. There is an exit exam for graduating from high school and many students proceeding to the university level are required to take the College Scholastic Ability Test that is held every November. Although there is a test for non-high school graduates, called school qualification exam, most Koreans take the test.
Seoul is home to various specialized schools, including three science high schools (Hansung Science High School, Sejong Science High School and Seoul Science High School), and six foreign language High Schools (Daewon Foreign Language High School, Daeil Foreign Language High School, Ewha Girls' Foreign Language High School, Hanyoung Foreign Language High School, Myungduk Foreign Language High School and Seoul Foreign Language High School). Seoul Metropolitan Office of Education comprises 235 College-Preparatory High Schools, 80 Vocational Schools, 377 Middle Schools, and 33 Special Education Schools as of 2009.