A couple of years ago, I had a 12-hour layover in Seoul, Korea. I took the opportunity to sign up for a tour of downtown Seoul. As it turned out, the most interesting portion of the tour was Cheonggyecheon, Seoul’s urban stream. It is a popular and impressive accomplishment.
By Ken Otterbourg 
On a hot and hazy afternoon, I set off to walk the 4-mile length of Cheonggyecheon, the lovely ribbon of water that unfurls with quiet assertiveness through the heart of Seoul.
In the city’s preindustrial years, the stream was where lovers courted and women gathered to do wash. But Seoul’s boom after the Korean War brought shantytowns and pollution, and the stream became an eyesore. In 1958 a road was built over it. An elevated highway, finished in 1976, completed the entombment.
There Cheonggyecheon might have stayed, if not for serendipity and politics. Throughout the 1990s, a small group that included academics and engineers sought to uncover the waterway. They figured out how to manage the stream’s hydrology and mitigate the traffic snarl that might ensue when the highway and the road below, which carried more than 170,000 vehicles a day, were removed.
The missing component was a leader with clout. That person arrived in the form of Lee Myung-bak, a former construction executive whose company had been the principal contractor in building the highway. He made the stream’s restoration a key issue in his successful campaign for mayor of Seoul in 2002. (Five years later, he was elected president of South Korea.)
Work on the $372 million project, a reclamation job of mammoth proportions, began in 2003. First the elevated highway was torn down. Then the surface road was ripped up, again exposing the stream. Like many restorations, this one is not entirely faithful to the past. The stream was intermittent, barely trickling in the dry months and surging during the summer monsoon. Thanks to pumping stations that deliver more than 30 million gallons a day from the Han River, the stream now babbles reliably.
“People criticize this as a man-made river or fish tank,” Lee In-keun, a wiry and animated man, told me as we strolled the upper portion of Cheonggyecheon. The paths by the stream were crowded with people enjoying the water and pointing with delight at carp idling in the deeper pools. Research shows it provides a cooling effect during Seoul’s steamy summers. Lee oversaw the restoration project and agrees that Cheonggyecheon is artificial. But that distinction doesn’t matter to him; he finds the presence of nature as vital as in a truly natural setting.
It’s a jewel of the city. You can hear the water flow in the central area of ten million people. It’s unbelievable. We made that intentional.
Cheonggyecheon begins in the financial district, within a canyon of office buildings. The stream flows east, the banks widen. The concrete gives way to thatches of reeds and glades of trees. It moves past glitzy shopping areas and tired-looking wholesale districts and gigantic apartment complexes that rise up like fortresses. At one point a pair of concrete abutments appears in the stream. Part of the old highway, they are reminders of the past and the importance of engineering. Many Seoul residents find it hard to remember a time when the stream was covered, when herons didn’t wade gingerly in the water hunting for fish, when it wasn’t an inviting place.
 National Geographic (Apr 2016)