Gwangmyeongmun Gate was once the south gate at Deoksugung Palace. It contains a water clock, a hanging bronze bell from 1462, and a rocket cannon. The gate, which resembles a pavilion once led to Hamnyeongjeon Hall, where the king resided.
In 1938, during the occupation, the Japanese moved the gate near Seokjojeon Hall. At this time, the hall was being expanded.
Inside the structure is a water clock, bell, and cannon. The water clock, which is automatic striking, is known as Jagyeokru. The bell, forged in 1462 during the Joseon Dynasty, is from Heungcheonsa Temple. The cannon, which can be wheeled, uses gunpowder and can fire 100 arrows at the same time.