Busan is the biggest metropolitan area in South Korea after Seoul.
It is also one of the farthest big cities from Seoul.
It takes around three hours from Seoul to Busan using high-speed KTX trains.
(The KTX fare between Seoul and Busan costs around $50 USD or 55,000 won.)
Busan, used to be known as Pusan, is relatively close to Ulsan and Daegu.
Busan Metropolitan City is South Korea's biggest port and the fifth largest port in the world in terms of container trade.
Many Japanese tourists travel to Busan because it is the nearest city between South Korea and Japan.