South KoreaSouth Korea, officially the Republic of Korea, is a sovereign state in East Asia, constituting the southern part of the Korean Peninsula. The name Korea is derived from the ancient Kingdom of Goguryeo, also known as Koryŏ.Seoulofficially the Seoul Special City – is the capital and largest metropolis of South Korea.Busan, officially Busan Metropolitan City, romanized as Pusan before 2000, is South Korea's second-largest city after Seoul, with a population of approximately 3.6 million.The Nakdong Riveror Nakdonggang is the longest river in South Korea, and passes through major cities such as Daegu and Busan.Hallasanis a shield volcano on Jeju Island of South Korea. Hallasan is the highest mountain in South Korea.The Korean Demilitarized Zoneis a strip of land running across the Korean Peninsula. It was established at the end of the Korean War to serve as a buffer zone between North and South Korea. The DMZ is a de facto border barrier that divides the Korean Peninsula roughly in half. It was created by agreement between North Korea, China and the United Nations in 1953. The DMZ is 250 kilometres (160 miles) long, and about 4 kilometres (2.5 miles) wide.