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Join Date: Sep 2009
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Instead of assuming that you'll take the train to Seoul Station, I'd consider the airport limo bus stops too. For example, there's very frequent (every 15-20 minutes) service to the Westin Chosun which is very centrally located for lots of tourist things.
Going to Seoul very early in the morning avoids traffic issues, but there might be more reason to take the train if you're going back to the airport in rush hour.
The train stops in a university area, IIRC a couple stops before Seoul Station. This could be an interesting and relaxing area to explore, but if this is your first visit, I'd suggest heading for the main tourist attractions that are near the Westin.