Seoul Plaza's 1,000-Pyeong Underground 'Secret Space' Unveiled After 40 Years

Total Length of 335m on the Track from Euljiro 1(il)-ga Station to City Hall Station
Part of the Subway Station Innovation Project... Recruiting Citizen Explorers

Located 13 meters beneath Seoul Plaza in front of Seoul City Hall, a hidden underground space spanning 1,000 pyeong (3,182㎡) that had been concealed for 40 years has been revealed. This massive space, measuring 9.5 meters wide, 4.5 meters high, and 335 meters long, is situated beneath the nation's first underground shopping mall, 'City Star Mall,' and above the subway Line 2 tracks between Euljiro 1(il)-ga Station and City Hall Station. Above it runs an old drainage system, where stalactites?typically found in caves?have formed, and due to the subway, loud sounds reaching 80 dB occur every 4 to 6 minutes. Since the purpose and time of construction remain unknown, the place feels even more secretive and unique.

A Seoul city official stated, "It is presumed that this space was created to connect the subway Line 2 stations City Hall and Euljiro 1(il)-ga, which are at different heights."

Subway Station Innovation Project at City Hall Station and Others: "Developing Content for Citizens and Tourists to Enjoy"

Seoul announced on the 5th that this secret space will be open to the public from the 8th to the 23rd. This project is part of the ‘Subway Station Innovation Project,’ which aims to transform subway stations themselves into urban landmarks by reflecting local characteristics and trends. The goal is to repurpose subway stations, which have so far been used solely as transportation hubs, into software spaces where citizens and tourists can enjoy and linger.

The Subway Station Innovation Project is being carried out at four locations: Yeouinaru Station, which is being developed as a runner station; Sindang Station, transforming into a cultural hotspot for the MZ generation; Munjeong Station, offering unique sports experiences; and City Hall Station. A Seoul city official said, "Especially City Hall Station, as the heart of Seoul and an urban hub imbued with citizens' joys and sorrows, will have its purpose determined and commercialized based on citizens' ideas and proposals."

Veil Lifted on Secret 1,000-Pyeong Space Beneath Seoul Plaza... Seeking Utilization Plans Through a Contest

The course, which allows visitors to tour the underground space at City Hall Station, follows the route Seoul City Hall Citizen Hall → City Star Mall → Hidden Space → City Hall Station → Urban Architecture Exhibition Hall, and is open to everyone. Participants receive background information and safety training about the underground space at the Citizen Hall beneath Seoul City Hall, then pass through City Star Mall and Euljiro 1(il)-ga Station before descending to the second basement level to begin the full exploration.

All explorations are accompanied by a guide who shares stories hidden throughout the space. For example, the City Star Mall (formerly Sae Seoul Underground Shopping Mall) was the first underground shopping mall established in Seoul in 1967, marking a turning point in the transformation of the city's underground spaces. The structure connects the subway tracks and the shopping mall within the station, and with the opening of Line 2 (Euljiro 1(il)-ga to Seongsu), Sae Seoul Underground Shopping Mall and Eulji Underground Shopping Mall became the longest underground shopping malls in the country.

Meanwhile, Seoul is also running the from the 6th until next month’s 10th to gather citizens' ideas and proposals on how to utilize this space. Through this contest, the city hopes to receive creative ideas for ▲vertical connections between Seoul Plaza and the underground space, ▲efficient horizontal connections between City Hall Station, the Hidden Space, and Euljiro 1(il)-ga Station, and ▲unique underground space development, enabling citizens to fully enjoy and benefit from the area.

Hong Seon-gi, Seoul’s Future Space Planning Officer, said, “This is an opportunity to see and walk through an underground space beneath Seoul Plaza that no one could have imagined, discovering hidden stories and history within the city. We plan to develop City Hall Station and other urban underground spaces into areas reflecting citizens’ lifestyles and turn them into new attractive content for Seoul.”

This content was produced with the assistance of AI translation services.