Transit cards: T-money vs Climate Card

Two cards cover Seoul's subway and buses. T-money (recommended for most travelers) is a rechargeable pay-as-you-go card: buy it at any convenience store (CU, GS25, 7-Eleven, Emart24) or a subway station machine for about ₩3,000 empty, top it up with cash at the counter or machine, then tap on entry and exit on the subway (and when boarding and leaving buses, for transfer discounts). It works nationwide — other cities, buses, many taxis and even convenience-store purchases. The Climate Card (기후동행카드) is instead an unlimited Seoul pass, with tourist options for 1 / 2 / 3 / 5 / 7 days (₩5,000–20,000). You buy and charge it at Seoul subway station machines or customer centers (Android phones can also use a mobile version), then ride unlimited within Seoul. Important: it covers only Seoul's own subway and city buses — NOT the airport railroad (AREX), the Shinbundang line, trips outside Seoul, KTX or taxis. Bottom line: choose T-money for simplicity and nationwide use; the Climate Card only pays off if you stay a few days in Seoul and ride a lot (roughly 4–5+ trips a day).