Hanyangdoseong Museum explains Seoul's old city wall, from its Joseon-era construction to the fragments that still shape walks around the centre today. The subject is narrow, but it is a useful stop before walking the wall sections around Naksan, Dongdaemun, or the northern hills.
The museum works best as context rather than a stand-alone highlight. Visit it before a wall walk and the stones around central Seoul start to make more sense.