Running through the centre of Seoul there is a stream diving the city into north and south. Originally the Cheonggyecheon stream was formed during the Joseon Dynasty in order to provide drainage for the city, but after hundreds of years, in the 1940s, the city became so populated that a shanty town started growing around the stream and began polluting the area. It was covered over with concrete, and by 1976 a 5.6 km elevated highway had been built on top of it.
In 2003, however, as part of an urban renewal project, the highway was removed and the stream was recovered and turned into a beautiful 5.8 km urban park.
The Cheonggyecheon Restoration Project took two years and cost around $281 million and has created a beautiful stretch of green public space in the middle of the city.