Seoul’s subway system has sprouted 3 new lines from the time I arrived at the end of 2009, to present (mid 2011). Building is still underway, so that by 2013, there should be extensions to the current lines 3 and 9 (orange and gold).
Earlier in 2011, the full length of the airport railroad was finally opened, starting at Seoul station, which along with overland trains to all areas in South Korea, also connects subway lines 1 and 4 (dark and light blue). It travels through some major tourist areas such as Hongik University (Hongdae area), and also connects Gimpo Airport, before terminating at Incheon Airport. Riding the full length, including and transfers prior to entering the airport railroad (provided you complete your transfer within 30 minutes) should cost roughly W5000 ($5). See T-Money card for more information.
Line 2 (green) is the circular line, traversing central Seoul.
Line 3 (orange) runs from the north west to the south east, Line 4 (blue) from north to south, Line 5 (purple) from east to west, Line 6 (brown) from north west, through the centre, but keeping north of the river, to the north east, Line 7 (dark green) from north east to south west, Line 8 (pink) is confined to the south east and Line 9 (gold) from east to west keeping south of the river.
There are other lines that head outside the city or deal with the extremities of the conurbation which I will detail in a different post.
Using the subway system could not be simpler. Look for the touch screen machines by the entry gates inside the subway station. There are options in English, Japanese and Chinese, as well as Korean. For single travel, prices start from W1500 ($1.5), although W500 of the fare is a deposit for the orange travel ticket you will receive.
After completing your journey and exiting the gate in your destination station, look for the ‘Deposit Refund Device’ machine, insert the orange ticket, and it will spit out W500 for you. These are usually situated next to the ticketing machines and are clearly labelled.
The general rule for the fare is any journey under 10km is W1000, then you pay a little extra, usually W100 per additional 5km. Bus fares are similarly priced.
If you are staying in Seoul for a week or more, you might consider buying a T-Money card, as you will likely save money using it on public transportation, however you probably need to make about 20 individual journeys before you start to save money.