Saenamteo Cathedral which is located at 80-8 Ichon Avenue/Ichonno, Ichon-dong 199-1 beonji, Seoul Yongsan-gu was a former military camp that served as a place for execution of opponents of the Joseon Dynasty and these include the Korean Catholics.
It is also the place of martyrdom of many Christians among whom MEP fathers (Foreign Catholic Mission of Paris) but also the first father sent to Korea by the Chinese at the request of the Korean faithfuls (a Chinese father Ju Mo-moon) in 1801, the first native Korean Catholic Priest St Andrew Kim Dae-geon in 1846 (canonized by Pope John Paul II in 1984 with 102 other martyrs).
Many MEP fathers were executed including 2 bishops and 5 fathers (3 in 1839 and 4 in 1866) who were canonized in 1984. The MEP martyrs of 1839 were : Bishop Imbert (2nd Bishop of Korea), father Maubant and father Chastan MEP who were first MEP missionaries in Korea (as later for Bishop Daveluy -See Galmaemot- they surrendered to avoid a massacre).
The basilica was built in Korean style, which is uncommon architecture built in East Asia. Most of basilicas around the world built in Western style.
Holy Relics of 9 Saints are present in the crypt. 8 of this Saints were executed in Saenamteo : 3 French missionaries tortured in 1839, 4 French missionaries tortured in 1866 and Korean father Andrew Kim Dae-geon. The 9th Saint is a layman Korean martyred in 1866 at the South Gate of Seoul.