After the Korean War, millions of destitute people swarmed into Seoul in 1953, and the stream's edges became notorious slums with squatter housing on either side. It was a health hazard, the stench of raw sewage was overpowering and something had to be done.
First they piped it and turned it into a road, and then came the elevated motorway. But, by 2000, the flyover was an eyesore, vehicle pollution was also a health hazard and the people were screaming out for more green areas.
Enter new mayor and engineer Lee Myung-bak who ordered the dismantling of the motorway and restoration of the stream. Started in 2003, the job was so huge it was completed only last year.
It is truly lovely, and I spend a sunny morning walking its banks before strolling to Insadong, Seoul's arty heart. Here, art galleries, souvenir shops, art supply shops, and others selling richly textured handmade paper line a long pedestrians-only street.
Portrait painters whip-up great likenesses, fortune tellers reveal all, a calligrapher can write your name using images of flowers, and buskers and street actors frolic. At wheel-in stalls, busy ladies knock out hot pastries dripping cinnamon sugar syrup.
The side alleys are home to traditional teahouses and restaurants. After hours of walking, I recline in a teahouse carved from ancient dark wood with a swooping tiled roof. Elegant, whimsical music quivers through this calm room as I sip tea, shielded from the busy city outside.
At the end of Insadong, Gyeongbokgung Palace hides its imperial beauty behind a tall brick wall. The first sight of a Korean palace is breath-stealing with their soaring-wing tiled roofs, and wooden eaves and walls painted in strong crisp Buddhist colours of green, blue, coral, black, gold and white.
This palace complex with its many halls, pavilions, gardens and courtyards sprawls over 12ha. Nearby, a grand, airy lakeside pavilion is where the royal family entertained on long summer evenings.
This is only one palace complex, of one dynasty, and there are three more equally as impressive. I lose an afternoon at Changdeokung Palace, 10 minutes walk away, strolling through its 32ha park of woodlands, lakes, pavilions and pagodas. It's another world of low, elegant, ancient buildings, paths meandering through 400-year-old forest, birdsong in secret valleys, butterflies and dragonflies winging around lotus flowers.
This hidden garden is so quietly, beautifully Zen that I have to remind myself there are 12 million busy people outside its tall enclosing walls.
I spend four more days in Seoul, peeling back its layers, hanging out in parks people watching, visiting more hidden palaces, the herb market, the trendy fashion area, and eating. I snack from street stalls, relish the busy smoky ambience of barbecue restaurants and enjoy decadently lengthy meals with 15 delicate courses. Korean food, predominantly vegetables and seafood, is deliciously fresh, tasty and spicy. I cross the stream many times and walk along its banks. I enjoy the fresh smell of water and the sound as it rushes over rocks and dances down fountains.
In the evenings I gravitate to it, with thousands of other Seoul seekers out strolling. Finally Seoul has a heart.
IF YOU GO
Getting there: Korean Air flies direct between Auckland and Seoul every day.
* The best time to visit is spring or autumn. The winters are freezing and the summers are baking warm.
* Get around on the superb, easy-to-follow underground rail system.
* Seoul has a range of accommodation from luxury to backpacker. See the Lonely Planet guide or search the net.
Further information: See tour2korea.com.