The project, named Seoullo 7017, is a kilometre-long path featuring 24,000 trees, shrubs and flowers set into cylindrical planters.
The pedestrian-only route extends across several lanes of traffic to connect Seoul Station and Namdaemun Market with the city's Malli-dong, Jungnim-dong and Cheongpa-dong neighbourhoods.
Dutch firm MVRDV was selected to design the walkway as the result of an international competition.
Once destined for demolition, the 16-metre-tall highway is now connected to surrounding hotels and shops by a network of bridges and stairs.
The planters are ringed with blue lighting that illuminates the walkway at nighttime. The hue of the lights can be adjusted for different events and festivals.
Future plans for the route include links to "satellite" gardens and to street level, as well as the potential for the planters to be used as an "urban nursery", growing trees and plants to be transported elsewhere in the city.
While the project has attracted comparison with New York's High Line, it differs in that it forms part of a string of major urban design interventions instigated by the mayor's office to make Seoul more pedestrian friendly.
The majority of these projects came about following the appointment of Seung H-Sang as Seoul's first city architect in 2014.
This movie is part of Dezeen x MINI Living Initiative, a year-long collaboration with MINI exploring how architecture and design can contribute to a brighter urban future through a series of videos and talks.