The wall has names
Seosan's Haemieupseong first looks like a Joseon-era stone fortress enclosing an open green space. Look more carefully at the masonry, however, and you may notice place names such as Gongju, Cheongju and Imcheon carved into individual stones. These inscriptions are called gakjaseok (각자석).
Who built this part?
Seosan City's cultural facilities office explains that different towns were assigned portions of the wall and carved their names to identify responsibility for the work. Rather than treating the fortress simply as scenery, imagine the communities and workers involved. Do not assume every inscription is visible along the entire route today.
From garrison to local town
Construction took place from 1417 to 1421. The fortress served as the center of a regional military command, before that command moved to Cheongju in 1651. The site then functioned as a walled administrative town. The city also points to an inscription associated with a 1491 repair at the southern gate, Jinnammun.
Remember the people imprisoned here
The reconstructed prison and an old pagoda tree also recall the persecution of Catholics in late Joseon Korea. This is not merely a picturesque backdrop: approach the memorial spaces with care and read their historical explanations.
Before you visit
The location is 143 Nammun 2-ro, Haemi-myeon, Seosan-si, Chungcheongnam-do (search 서산 해미읍성). Seosan City's posted visitor hours are 05:00–21:00 from March through October and 06:00–19:00 from November through February. Because the city page was last updated in January 2023, verify current access with the management office at +82-41-661-8005 before a 2026 trip. The city's listed Saturday traditional performances run April–October, not automatically in November. Current transport schedules, activities, admission charges and restrictions have not been independently verified.