Pungnaptoseong Earthen Fortress, Seoul

Between the apartment blocks of Pungnap-dong in Songpa-gu runs a long, grassy ridge. It looks like an embankment, but it is a massive rammed-earth wall built by the Baekje kingdom on the bank of the Han River. As excavations have continued, the view that Pungnaptoseong was the first royal city of Hanseong-period Baekje has become the academic consensus, and you can walk the remains of Seoul's oldest city as casually as a neighbourhood stroll.

A royal city revealed by a flood

The fortress first drew attention after the great flood of 1925. The swollen Han River swept away part of the west wall, exposing high-status finds such as a Chinese bronze cooking pot with a handle and belt ornaments. It became a national Historic Site in 1963, but only the walls were protected, and the area inside was built over with housing.

The turning point came in 1997, when Baekje pottery turned up on an apartment construction site. Later digs inside the walls uncovered large building foundations, roads, clay pipes thought to be a water supply and the earliest Baekje tiled building found above ground. At the Gyeongdang site, archaeologists found a ritual complex along with 12 horse skulls, apparently offerings, and a jar inscribed with the title "daebu", a court rank.

A bigger wall than you'd imagine

The original circuit was about 3.5 km, but the west wall facing the river has been lost, leaving roughly 2.1 km today. Excavation showed that the base of the wall was 43 m wide and more than 11 m high. Builders first laid a foundation of tidal mud, then rammed layer after layer of clay and sandy soil, reinforcing parts with plant material and gravel. Where roads cut through the wall, you can see these layers in cross-section.

Walking the walls

• East and south walls: the east wall is the longest surviving stretch, with paths alongside it; continue along the south wall towards the Olympic Bridge.
• Gyeongdang site: the excavation area with its ritual remains, wells and storage pits, now landscaped as a park.
• Pungnap Baekje Culture Park: 4th–5th-century roads, 4 m wide and laid out in a grid, plus traces of an inner wall.
• West wall excavation: digging continues to trace the lost west wall, and you can follow progress through the fence.

A debate still going on

When and by whom the walls were built is still being researched. In 1939 one scholar argued it was a military fort rather than a royal city, and when Baekje finds turned up at Mongchontoseong to the south in the 1980s, opinion split over where Wiryeseong, the first capital, really was. Radiocarbon dating places construction between the 2nd century BC and the 3rd century AD, and estimates that close to a million person-days of labour went into the walls are often cited in favour of the royal-city theory. With each new excavation, the evidence has leaned further towards it.

Tripto tips

• Visiting: free and open all year.
• Time needed: 60–90 minutes for the east and south walls and the two parks.
• Getting there: from Cheonho Station (Lines 5 and 8), Exit 10, it is about 120 m to the entrance of Pungnap Neighbourhood Park, where the wall begins.
• Best time: spring and summer, when the grass on the walls is green, or around sunset.
• Nearby: the Hanseong Baekje Museum in Olympic Park to the south has a reconstruction of the wall's cross-section, which makes the structure much easier to understand after your walk. Mongchontoseong, another Baekje fortress, is in the same park.