The Millennium Hilton was renovated extensively a few years ago and is not so far from "the action" as other posters claimed. A few minutes and you are already at Namdaemun markets and the nearest subway station.

In the other direction, new real estate development around the Korea Development Bank building has brought quite nice restaurants and shops within walking distance.

And the buffet at the Japanese-Korean restaurant "Genji" within the Hilton is still one of the best in Seoul.