Cheonggyecheon was originally the drainage of Joseon-era Hanyang. It collected water inside the city walls and carried it east, and dredging it against monsoon flooding was a matter of state. As the city expanded in the 20th century, shanty housing crowded its banks and sewage ran in. Covering work began in 1958, the stream disappeared beneath concrete, and by the 1970s an elevated expressway ran above that. A waterway became a road, and the road gained a second storey — which at the time read as a symbol of modernisation.
The decision to restore came in the early 2000s. Safety concerns about the elevated expressway coincided with shifting attitudes toward the urban environment; demolition started in 2003 and water returned in 2005. It was not, however, a return to a natural state. Upstream flow is insufficient, so water is brought in and released along the channel, which leaves an open argument about whether this counts as restoration or an artificial canal. Walking it, you get the impression of a well-designed urban waterfront park rather than a river — and that impression is not wrong.
The walk changes character by section. The Gwanghwamun end has the waterfall and a plaza and draws the biggest crowds; a little further down you pass beneath bridges past tile works and lighting. Toward Dongdaemun the surroundings turn into shops and markets and the mood gets busier, and beyond that the path leaves downtown for quieter stretches. Few people walk all 11 km; two hours or so from Gwanghwamun to Dongdaemun is the common version.
What Cheonggyecheon means to Seoulites is less about scenery than temperature. Flowing water and a level below the roadway make this corridor perceptibly cooler than the streets beside it in summer, so on midsummer evenings people line the edges with their feet in the water. Winter brings a lantern festival with sculptures floating on the surface, and in spring and autumn office workers walk it at lunch. It is less a tourist site than a piece of daily downtown life, which is exactly why even a short stop shows you Seoul's ordinary rhythm.