Korea Pass (www.lottecard.co.kr/app/html/koreapass/IHKPAZZ_V100.jsp) is a prepaid card, available in denominations from ₩50,000 to ₩500,000, that provides discounts on a range of goods and services. It can be bought at Lotte Mart and 7-Eleven branches in Seoul as well as at the A'REX booth at Incheon International Airport.
Discover Seoul Pass (www.discoverseoulpass.com) If you're planning on cramming an awful lot of sights into a short of space of time, Seoul's official tourist discount card is just about worth the outlay. Available in 24-hour, 48-hour or 72-hour versions (₩39,900/55,000/70,000), it gets you free or discounted entry into dozens of attractions all over the city. It also works as a rechargeable transport card on subways and buses. Buy it from CU convenience stores inside Incheon Airport, or from Tourist Information Centers throughout the city. You can also purchase it from the website as a mobile app.