When I booked my flights for Asia, I decided to treat the 12-hour layover in Seoul, South Korea on the way back as an opprotunity. After all, how many times do you connect through a city you’d love to explore, let alone one halfway around the world?
The little bit of research I did revealed that there was a tourist information desk at the airport that was a good resource. My overnight flight from Vietnam arrived before they opened, so I had a chance to grab breakfast and brush my teeth before the very helpful (and English-speaking!) woman gave me some pointers.
Her suggestion: take the bus downtown, and ride and hop-on hop-off tourist bus circuit to over 2 dozen sites. It worked quite well; the downtown bus was a full coach with incredible legroom for the 1.5 hour trip from Incheon airport into downtown Seoul. The tourist bus was right there, and stops at several palaces, markets, and museums. And they even take care of you if you lose your ticket because your brain is only running at half power 
My first stop was Deoksugung Palace, which was more oriental than any others on the trip. They also do an intricate traditional changing of the guard, which amusingly happens with Dunkin Donuts as a backdrop. Dozing off on the next bus ride convinced me to get some lunch at Itaewon, a street full of western chain eateries and stores. Behind them, though, was Buddha Belly and some decent Thai curry and lemongrass tea. (After thinking how nice it would be to have some cold weather after all the heat, I got more than I bargained for with a windy 52-degree F day and desperately needed to warm up.)
Then it was onto Nasamgol Traditional Village, a collection of classic homes overrun by school kids and couples taking part in a traditional marriage ceremony - robes, live chicken, and all. Riding up to the top of Mt. Namsan behind the village took me to the N Seoul Tower’s high observation deck, where I even managed to spot a few of the day’s destinations.
Back at the bottom, I started to get nervous - I still had to ride the last half of the tour bus circuit, and then catch the airport bus, check in, and clear security - and it was starting to get late. The buses made good time, though, so I got to breathe a sigh of relief and look forward to finally sleeping in my own bed again.
Overall, it was a good day; the city is much more modern and sane than those of the last 3 weeks and fairly tourist friendly - not a bad place to spend a day layover.
