The Cheonggyecheon stream was formed during the Joseon Dynasty in order to provide drainage for the city. It lasted for hundreds of years until the 1940s, when the city became so populated that a shanty town popped up around the stream and began polluting the area. The stream was gradually covered over with concrete, and by 1976 a 5.6 km elevated highway was built on top of it.
Considered an example of ‘successful industrialization and modernization’, the highway remained there until 2003, when city planners tore it down to revitalize the area and help Seoul remake itself as a modern environmentally friendly city. The Cheonggyecheon Restoration Project took two years and cost around $281 million, but it has created a thriving stretch of green public space in the middle of the city.