Onseong

Onsŏng stands on the Tumen River, where low ground along the water gives way to the hills of Korea's northeastern frontier. In 1440 King Sejong's government established the county as part of the Six Garrisons created under Kim Chongsŏ, bringing settlers from towns farther south. Fortifications guarded the river approaches, including the walled town itself. In 1608 its stone defences were rebuilt in earth on a larger circuit.