i stayed at the hyatt at the airport and never left on my 23 hours in S...

you can organize things from there...

remember you really do not have a full day for activities

My husband just got back from a 4 night stay at the Park Hyatt. He really liked the hotel but was there on business so didn't explore much apart from on Sunday when he had a day off.
His room on the 20th floor overlooked the Olympic stadium.
His only negative comment was that you can see into some of the other rooms (floor to ceiling windows and the rooms are angled so that some rooms have little privacy but there are blinds)

He did eat at the hotel breakfast buffet every day and especially enjoyed the eggs which they cook to order. One of the amenity gifts he received was a bottle of Hwayo (a Korean spirit a type of soju?) which he brought home and it's deliciously fragrant and has a mild fresh citrusy flavour.

It took about 45 mins to reach the hotel from the airport.

I spent two weeks in South Korea without doing the DMZ tour, and did not regret it. with such a short time in Seoul I would concentrate on the city itself.

The Westin Chosun is in the ideal location in the heart of the old city and if you are using spg points is where I would stay to be close to sites and good walking all around you. We have stayed 5 nights at the Westin Chosun and 3 nights at the Park Hyatt. The PH is located across the river in the new section of Seoul(which has all been built out of farmlands in the last 15-20 years) across the street to a very large mall(IIRC the largest in Seoul)but besides that, not much of interest around in walking distance so we had to use the taxi to get around on that side of town. The W Walker Hill is not well located. All that said you might want to take rhkkmk's advice and stay at the Hyatt Incheon which is right next to the airport with a free shuttle every 20 minutes. We took the Park Hyatt limo to the airport about 08:30 in the morning and with rush hour traffic it took us about 110 minutes to reach the airport and my guess is that it would be worse in the afternoon traffic hour as Seoul rush hour traffic can be a nightmare.

Aloha!

Thank you al for the replies; as usual, very helpful. I am still playing with my air itinerary, and this free stopover may go away. If I do it, I think I will stay somewhere central, and try to just enjoy the city for a day (and forego the DMZ tour).

My 24 hour layover has turned into a 9 and a half hour layover. Arriving at around 7 am, and leaving at 4:30 pm. Maybe I can take a city tour or something like that(?).