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Start by looking at the subwway map. If the hotel is located very close to a subway station, especially if you can get to the tourist areas without changing subway lines, the hotel could work very well, although IMO D-Cube is too far/too long of a ride to do often.
Also IMO parts of Gangnam are interesting for walking, generally those areas close to the river and not back from CODEX, although they're not on the top of lists of tourist attractions.
A lot depends on how long you will be in Seoul.