You may want to go to the restroom. Subway stations have signs that tell you which direction the restrooms are -- and how far away they are. The distances are marked in meters. For those folks from the United States who don't think in terms of meters, think "a meter is a little more than a yard," and you'll be fine.

You'll see vending machines that look like this near the restroom. These machines sell toilet paper, which is not normally provided in the restroom. This particular machine requires 200 Won, and only accepts 100 Won coins.