This is where the Korean Catholic community was first born and where the remains of many martyrs are buried. In the 2,000-year history of the church, the Korean Catholic Church was founded by Koreans themselves, which is unprecedented. The origin of the Catholic Church in Korea can be said to be in the spring of 1784 when Lee Seung-hun returned to Korea after being baptized in Beijing. However, four years earlier, in January 1780, a lecture series centered around Kwon Cheol-sin was held at Cheonjinam, where prominent young scholars encountered Catholicism. Old Myeongdong Cathedral That fall, Kim Beom-woo, an interpreter living in Myeongrye-bang, Seoul, was influenced by them and converted to Catholicism, opening church ceremonies and doctrine classes at home. By doing so, he laid the foundation for the salvation of the people in the heart of the capital city. Today, the Myeongdong Cathedral, the living history of the Catholic Church in Korea, stands here.

Over a hundred years after the founding of the Catholic Church in Korea in the fall of 1784, countless Catholics were executed at the intersection outside Seosomun. On August 16, 2014, Pope Francis visited the Seosomun Intersection Martyrs' Shrine before the Gwanghwamun beatification ceremony. At the beatification ceremony held afterward, he declared 'Yun Ji-chung and 123 companions' as beatified. Of these, 27 were martyred at the intersection outside Seosomun. Therefore, regarding church history, the Seosomun Negeri Martyrs' Site has become the largest martyrdom site in Korea, producing the most significant number of saints and blessings in a single location.

Saenamteo is a sandy beach on the Han River, and its name comes from the word saenamu-teo, which means grass and trees. It is the place where Roman Catholic priests such as Fr. Ju Moon-mo in 1801 and St. Andrew Kim Dae-geon in 1846 were martyred, and a Catholic church was built in 1987 to commemorate the martyrdom. Construction began in 1984, the 200th anniversary of the founding of the Catholic Church in Korea, and the Saenamteo Memorial Church was built in three years. It is a representative martyrdom site in Korea where 11 out of 14 priests in the history of the Catholic Church in Korea were martyred. From 1801 to 1866, 11 shepherds, including 10 foreign priests, shed their blood as martyrs here. If the intersection outside Seosomun is called the ‘martyrdom site of the laity,’ then this place can be called the ‘martyrdom site of the priests.’

Jeoldusan is a peak located on the east side of Yanghwajin, which was a transportation hub and training ground for warships during the Joseon Dynasty, as well as a place for executions, ancestral rites, and relief (to help the impoverished during famine). It was initially called Jamdubong because it resembled the head of a silkworm or Gaeuldu. The fact that this place, which Chinese envoys praised for its outstanding surrounding scenery, came to be called Jeoldusan because many Catholics were beheaded here is related to the execution of many believers during the Byeongin Persecution in 1866. In 1968, to celebrate the beatification of the 24 martyrs of the Byeong-in Persecution, a burial chamber for their remains was created in the basement of the memorial cathedral. The remains of 27 martyred saints and one unknown martyr are enshrined here.