Cheonggyecheon

Listen first. Under the hum of Seoul's traffic there is another sound here, low and steady. It is running water, moving over stone. Step down the stairs from street level and the temperature drops a little. The air feels cooler and damper. Car horns fade behind the stone walls. You are now standing beside Cheonggyecheon, a stream that runs through the centre of one of the busiest cities in Asia. For a long time, the people above you could not see it at all.

The name means, roughly, the clear valley stream. For centuries it was a natural waterway. It gathered rain from the mountains around the old capital and carried it east, out of the city. During the Joseon dynasty, the royal kingdom that ruled Korea for about five hundred years, this stream was part of daily life. Women washed clothes on its banks. Children played in its shallows. Bridges of granite linked the northern and southern halves of the city.

The stream also had problems. It flooded in heavy summer rains. It filled with silt and household waste. Historical accounts describe large dredging projects in the eighteenth century, when Joseon kings sent workers to clear the channel and strengthen its banks. So the idea of reshaping this waterway is not new. People in Seoul have been trying to manage it for hundreds of years. What happened in the twentieth century, however, went much further.

After the Korean War, Seoul was poor and crowded. Makeshift houses lined the banks, and the water became badly polluted. The city's answer was to cover the stream completely. Through the late 1950s and 1960s, it disappeared under concrete. Then an elevated highway was built on top of it. For many people at the time, this was a symbol of progress. Cars moved fast above, and the old, dirty stream was out of sight.

For decades, this was a corridor of noise and shadow. Under the highway, workshops and small markets grew up, selling tools, electronics, and machine parts. The road carried huge amounts of traffic. But by the end of the century the structure was ageing, and engineers raised serious concerns about its safety. The city faced a choice. It could repair the highway at great cost... or it could remove it entirely.

Seoul chose to remove it. The project began in the early 2000s, under the city's mayor at the time, Lee Myung-bak, who later became president of South Korea. It was controversial. Shopkeepers worried about losing their business. Drivers worried about traffic jams. Still, the highway came down, the concrete cover was broken open, and in 2005 the restored stream opened to the public. Here is the first surprise for many visitors — the water around you is not entirely natural.

The original springs and tributaries had been cut off long ago. So much of the flow is pumped in, using treated water from the Han River and groundwater from below the city. In other words, this is a stream that the city must actively keep alive. Some critics have called it an expensive artificial canal. Supporters point to cooler summer air, returning fish and birds, and a long green path through the city. Both views are worth keeping in mind as you walk.

The stream begins at Cheonggye Plaza, near the wide avenue that leads to Gwanghwamun, the main gate of Gyeongbokgung Palace. Look for the large spiral sculpture in red and blue. It is called Spring, and it was designed by the artists Claes Oldenburg and Coosje van Bruggen. Its shape looks like a seashell turning upward. Just beside it, water pours down in a small waterfall. This is the symbolic source, where the restored stream starts its journey east.

Walk a short way and you reach Gwangtonggyo, one of the oldest bridges on the stream. Look closely at the stones in the walls below it. Some of them are older and darker than the rest. When the stream was covered, many old bridge stones were removed or buried. During restoration, some were recovered and set back into place. That is the second surprise. In the middle of a modern design, you can find carved granite that Joseon builders shaped by hand.

Further along, one long wall is covered with a painted ceramic tile mural. It shows a royal procession from the Joseon period, with hundreds of small figures — soldiers, officials, horses, and banner carriers — moving in a long line. The mural is based on a famous record of a journey by King Jeongjo, an eighteenth century ruler. Walk slowly beside it. The figures change as you move, like frames in a very long film.

As you continue east, the city changes around you. The office towers near the plaza give way to older, lower buildings. Above the walls you will find the edges of the Dongdaemun area, with its giant clothing markets and fabric shops. Nearby is Gwangjang Market, known for food stalls and the smell of mung bean pancakes frying in oil. Many of the old trades that once lived under the highway still operate in the streets above.

The path itself is a place of small rituals. Office workers eat lunch on the stone banks. Couples sit with their feet near the water on summer evenings. Children cross the stepping stones, holding their arms out for balance. Herons sometimes stand very still in the shallows. In late autumn, the stream often fills with large glowing lanterns for the Seoul Lantern Festival, and the water carries their reflections in long lines of colour.

Far downstream, near the eastern end of the restored section, a few concrete pillars from the old highway still stand. They were left on purpose, as a reminder. Rough and grey, they rise from the ground like the bones of something large and gone. Beyond them, the stream continues toward other waterways and, finally, to the Han River. The whole route is long, and most visitors walk only part of it.

Before you climb back up to the street, pause for a moment. Look at the water moving past your feet. Notice the strip of sky between the buildings, a space that was once filled by a road. Listen again for that sound of water under the traffic. Every city chooses what to hide and what to show. Here, Seoul made a different choice. As you walk away, you may still hear the stream behind you, a little quieter with each step.