Seoul Plaza in front of City Hall has long been a symbolic stage for Korea’s political and social life, especially since its formal opening in 2004 as a planned civic square. Yet despite its visibility and frequent use for large events, it has struggled to support everyday life: long closures for setup and maintenance, separation from its surroundings by traffic and private developments, and a shift toward a “theater plaza” where opinions are performed rather than genuinely exchanged.

This project reimagines Seoul Plaza as an Event Horizon—a shared ground where events unfold, spread, and reconnect with the city. In parallel with Seoul’s broader vision for underground development, the proposal links the plaza to nearby urban flows and neighboring spaces, such as Gwanghwamun, creating a larger civic network. Above, the horizon stretches across the open square into the surrounding fabric; below, it begins in the subway, drawing people upward and outward. The sloped space between these two horizons becomes another everyday plaza within—different in form but still part of the same civic ground. In this redefined plaza, accessibility is prioritized over mere openness: it accommodates mass gatherings, minorities, and solitary walkers alike, fostering observation, encounter, and participation. Through continuous movement and circulation, the event horizon sustains diverse forms and scales of gathering, keeping Seoul’s public life fluid, inclusive, and alive.