Originally Posted by
SpeedAdvantage
How about if the layover is more than 10 hrs and the person would like to go out and see Seoul? I'm assuming KE will store check bags in the terminal. So you head to arrival, clear immigration with KE boarding pass? and take the bus/tour?
We picked up several English brochures @ICN (Welcome to KoreaFree Transit Tour) to reference it for future visit, since nobody else responded yet to this, I will try my best.
As you have 10+ hours, there are 3 tours of 5 hours in duration & should be good for you:
Seoul City Tour (08:00 - 13:00)
Seoul Cultural Tour (10:00 - 15:00) ** not offered on Mondays
Seoul Shopping Tour (13:00 - 18:00) ** not offered on Tuesday
Tour bus & guide are included, free. Application entrance fee ($3) and lunch ($7) in USD excluded - to be collected.
To book or sign-up for it, Passport, former (inbound) Flight Ticket/BP and next Boarding Pass required - go to the Transit tour Main Desk @ 1/F - Arrival Hall, No 41 & No. 42 counters, open hours 06:00 - 18:00
Email - transittour@airportkr
Tel +82-32-741-3139 or 3140, +82-2-6944-8464
From the departure floor, ask at the tour desk on 2/F or go to the transit tour desk on 1/F. Heavy luggage - you can put your luggage in the tour desk or in the tour bus until the tour ends. No, you do not need a transit visa. You have to fill out arrival card with your passport, and then go to the transit tour desk. Staff will help you with the process.
(My notes 
above info is taken directly from the brochure obtained - as we all know, it's all subject to change, please re/confirm with them on arrival.
AREX or Airport Railroad Express Train is the fastest way between ICN and Seoul with 43 minutes travel time, the "normal" train is slower. By taxi or non-stop bus, one hour is the minimum travel time from our experience. Having spent last week in Seoul, I can attest that traffic in & around the city is as bad as LAX, especially during the AM and PM rush.
Enjoy
