Sinmumun Gate guards the north of Gyeongbokgung Palace. The gate obtained its name in 1475, during the reign of King Seongjong, with the idea of “four guardian deities”. People believed there were spiritual beings to protect the four directions of east, west, south, and north, which were the blue dragon, white tiger, red phoenix, and dark tortoise, respectively. Since "Hoengmu" in Korean refers to the dark tortoise deity and "Sin" refers to the god, the gate is called "Sinmu."
The current Sinmumun Gate was rebuilt in 1865, along with the restoration project of Gyeongbokgung Palace. Considering it is close to the main gate of the Presidential Residence of Cheongwadae, it has been restricted from passing through since 1961 due to security reasons. Until 2006, it eventually reopened and currently serves as another gate of Gyeongbokgung Palace.
If you look up at the ceiling of the Sinmumun Gate, you can see there is a black tortoise drawn on it. Long before the Joseon Dynasty, there had been a concept of “four guardian deities” in the East. That’s why Sinmumum Gate was named to portray the black tortoise that guards the gate among the four guardian deities. It was constructed as “mysteriously outstanding martial arts”.
According to the yin-yang ideology, the north symbolized winter and death, which were classified as yin energy. Therefore, the Sinmumun Gate usually remained closed to block the yin energy from entering the palace. The gate sometimes served as a secret gate for the king to leave the palace. It was said that King Yeongjo often visited Yuksanggung Palace, where his mother’s shrine was located.
Most people enter through Gwanghwamun Gate and Geonchunmun Gate. Nevertheless, people nowadays using the Sinmumun Gate are increasing, as those entering from the gate can discover a new route to visit Gyeongbokgung Palace.