Jeoldusan in Hapjeong-dong, Mapo-gu.
It is said that during the Byeong-in Persecution, 8,000 Catholic believers were beheaded, and so it was named Jeoldusan.
Right next to it is the Yangwhajin Foreign Missionary Cemetery, [AKA Hanseong Foreign Missionary Cemetery].
Those who watched the drama "Mr. Sunshine" will probably be familiar with it.