We went on the Seoul City Tour bus and the first stop was N Seoul Tower. It stops just down from the entrance but be warned - the walk up to the entrance is STEEP! And I don't usually complain about walking far or anything. Of course in saying that, My Mum has a bad leg and she still made it so it's do-able, but it could take about an extra half an hour to your time here if you don't run straight up it.