In 2000, the aspiring mayor of Seoul set out to complete an audacious task: destroy an elevated highway used by almost 170,000 drivers a day and revitalize the faltering stream it had cemented shut for over six decades. Eight years after its completion in 2005, the Cheonggyecheon Restoration Project (“cheon” means stream in Korean) has quieted early critics and earned plaudits worldwide for its success as a sorely needed green space in South Korea’s largest city. The project’s greatest triumph is that it is not simply a static green oasis in downtown Seoul. It connects and integrates disparate neighborhoods into a cohesive urban fabric.

There are many specific things that make Cheonggyecheon a successful urban park, but one broad quality permeates the entire endeavor: walkability. In Walkable City: How Downtown Can Save America, Jeff Speck describes walkability as both an indicator of urban vitality as well as a contributor to it. Walkability allows the residents of a city to come together on foot. Speck argues walkable cities perform better than their auto-dependent peers in three important respects: wealth, health, and sustainability. In cities that are more walkable with a variety of transportation options, people are more economically efficient, healthier, and use less energy per capita.

Cheonggyecheon has proved no exception to these benefits. Since its completion, property values within 50 meters of the stream’s route have increased at twice the average rate in Seoul and over 500,000 pedestrians now walk in the area weekly. In addition, the area’s natural ecosystem has been restored and previously high temperatures caused by an urban heat island effect have dropped by an average of five degrees Celsius. Equally important, pollution levels for PM10, nitrogen oxide and benzene (which were above the Seoul average with the elevated highway) have been curtailed thanks to a shift from automobiles to transit. It is also worth noting the severe traffic bottlenecks forecasted by critics of the project have not materialized.

Cheonggyecheon’s success is due to its fulfillment of the “four keys to walkability.” It is useful, safe, comfortable, and interesting. Cheonggyecheon courses through Seoul’s heavily trafficked downtown, providing thousands of pedestrians unfettered access to green space and providing a natural bridge between the two large neighborhoods of Jongno and Dongdaemun. 22 bridges strategically crisscross the stream’s 5.8 kilometers; a large contrast to the relative paucity of crossings that existed when the elevated highway was still standing. In addition, the stream parallels several stops on line 1 of the subway and is long enough to provide access to stops on lines 2-5 as well.

The importance of safety is also apparent in the project’s design. Of the 22 bridges providing access to different neighborhoods, half are reserved solely for pedestrians, and half are auto/pedestrian mixed use. The stream features walking paths on either side that are recessed from street level down to the stream. Leafy plants and several feet of stone wall provide a natural barrier between the rumble of automobiles and street life above and the pedestrian experience below. Elevation changes along the paths are marked through color or texture contrasts in the stone used. Finally, the stream’s embankments were built with South Korea’s monsoon climate in mind, and are capable of handling extreme summer floods estimated to occur only once every 200 years.

Cheonggyecheon is also comfortable in the urban planning sense because it satisfies two important human needs: prospect and refuge. The stream has several different levels that allow individuals to survey from the elevated bridges or seek solitude and quiet conversation in the sheltered confines of the walking path. The bridges also provide shaded areas of vegetation in the hot summer months, as well as nooks in the embankments populated by art exhibits. On a basic level, it follows Jan Gehl’s exhortation to keep urban places small. The narrow width of the project encourages the density of activity that makes the major traffic artery feel used and alive.

Cheonggyecheon succeeds because it is interesting. It also succeeds because of its reserved use of green space. At a time when mayors in almost every city are scrambling to promote the next big urban park, it may seem odd to praise the opposite. Yet the relative benefits of smaller-scale green parks in urban areas have long been known. Jane Jacobs cautioned against giving up the density and diversity of human experience that give urbanity a natural advantage over suburbia. In Green Metropolis, David Owen states the unpopular but common fact that verdant green areas are often boring in large doses, especially compared to the lively street scenes associated with density. Urban parks are a necessary, beneficial part of a city’s social fabric, but only when they integrate with the city rather than existing separately from it.

Cheonggyecheon is large enough to be an urban icon and a pedestrian refuge, but small and strategically placed enough to be an urban corridor worth crossing through. It simultaneously silences out the urban street scene, while embracing it by showcasing rotating art exhibits, providing spaces to gather, and increasing pedestrian density. Large parks can spread human interaction too thin. Cheonggyecheon, in contrast, encourages it.