Seoul 2005: tearing down a highway to bring back a buried stream

Seoul's Cheonggyecheon stream had been buried under a concrete deck and a 5.8 km elevated expressway since the 1960s-70s; by 2000 the structure was unsafe, repairs were estimated at $90-95 million, and 169,000 cars a day brought pollution that doubled nearby respiratory illness.

Answer a broken highway by removing it: tear down the elevated road and deck to daylight a buried stream, betting a park beats a road at moving people and commerce.

From July 2003 the city demolished the expressway and deck, recycled 95% of the 1.14 million tons of demolition waste, held over 4,200 meetings with business owners and vendors, rebuilt bus and subway networks, and pumped treated Han River water to keep the stream flowing; the 5.84 km corridor opened on 1 October 2005 with 22 new bridges.

The restored stream drew 64,000 visitors a day and 23.4 million a year; small-particle air pollution fell 35%, species rose 639% (plants 62 to 308), corridor temperatures ran 3.3-5.9°C cooler than parallel streets, and land prices within 50 m rose 30-50% — double Seoul's average.

For almost half a century, Seoul's historic Cheonggyecheon stream ran invisibly beneath a concrete deck and a 5.8 km elevated expressway built to move traffic through the city centre. By 2000 the structure was decaying: engineers estimated $90-95 million just to repair it, and the 169,000 cars that crossed daily left residents twice as likely to suffer respiratory disease as other Seoulites.

Instead of repairing the road, Mayor Lee Myung-bak's administration chose to remove it. From July 2003 crews tore down the expressway and deck, recycling 95% of the 1.14 million tons of demolition waste, while the city held more than 4,200 meetings with worried business owners and vendors, added rapid bus lines and a smart card system, and treated Han River water to keep the revived stream flowing.

On 1 October 2005 the 5.84 km corridor opened with 22 bridges, waterfalls, wetlands and walking trails. Within three years it was drawing 64,000 visitors a day, plant species had grown from 62 to 308, small-particle air pollution fell 35%, and the corridor ran several degrees cooler than neighbouring streets — a park that worked harder than the road it replaced.

It reframed the problem: the question was not how to repair a failing road but what the road was hiding.

It bet on people and transit instead of cars, pairing demolition with bus and subway reform rather than hoping traffic would vanish.

It recycled the demolition itself — 95% of 1.14 million tons of waste — making removal part of the sustainable story.

It treated opposition as a design input, holding over 4,200 stakeholder meetings before and during construction.

It produced measurable wins across every axis at once: ecology, air quality, temperature, visitors and property value.

Removing infrastructure can be the boldest design move: when an asset decays, ask what it was hiding — daylighting the buried stream outperformed the road on ecology, air quality and land value.

Cheonggyecheon became a global reference for removing urban highways and daylighting buried streams, with the ADB case study noting that cities worldwide look to Seoul's turnaround. Its water is pumped and treated from the Han River, a point critics raise about its authenticity, and accessibility gaps were fixed only after protests, with elevators later added at seven locations. Two decades on, the corridor still draws tens of thousands of visitors daily and is credited with catalysing an estimated 22 trillion won of redevelopment investment in the surrounding area.