Deokjusansang Fortress is a mountain fortress in the valleys below Woraksan, with old walls following the folds of the slopes around Deokjugol and Songgye Valley. The remains are most interesting as part of a walk through the park rather than as a single preserved castle.
Use it as a historical layer on a Woraksan outing from Suanbo. The setting is the point: forest, stream valleys, and stonework that shows how defence here followed the mountain rather than fighting it.