Seoul sits in the north-west of the country, on the Han River. It has been Korea's capital since 1394 - more than 600 years - which makes it one of the oldest continually-living capitals on Earth. In the very middle of the modern city you can walk straight into five royal palaces, each set inside its own walled garden.
The biggest palace is called Gyeongbokgung. Twice a day, guards in bright red and blue uniforms march in front of its main gate, with drums, in a ceremony that has been recreated from old paintings. Visitors who wear a hanbok (traditional Korean dress) get into the palace for free.
Above and below the streets, Seoul moves fast. It has one of the busiest underground train systems in the world. The internet is fast too - South Korea has some of the speediest broadband on Earth, so a film that takes ten minutes to download in some countries downloads in seconds in Seoul.
Surrounding the city are forested mountains. From the top of Namsan, a small mountain right in the middle of Seoul, you can stand at the bottom of the famous N Seoul Tower and look out across glass skyscrapers, ancient palaces, and green hills all at once.