December changes central Seoul before the festival lights appear. Daylight ends earlier, the air turns sharper and the city moves from afternoon into night. That transition makes the route distinct from the same streets at other times of year, with light becoming part of how clients read the city.
During the festival, Cheonggyecheon adds illuminated sculptures, lantern-based displays and media art to the stream corridor. Water extends the effect through reflection, while bridges and street level offer viewpoints. The annual programme can change, so the route follows available sections rather than depending on one installation or fixed display.
