Seoul is an amazing city of around fourteen million people (twice the size of New York City). It's about a two hour bus ride from Seosan. The bus system is incredible in Korea. They are big and comfortable with leather high-back seats, TVs and air conditioning. It costs less than $10.00 to get from Seosan to Seoul.
There are dozens of separate areas to visit in Seoul including an area (Itawon) that is full of foreigners (like me) and home to many Western style restaurants. Seoul is a good place to shop, sightsee, eat good food, party and explore in general.
The public transportation in Seoul (and Korea in general) is second to none in the world, and it's cheap. You can get basically anywhere in the city of Seoul by subway for a dollar or two, or by taxi for just a few dollars.
Somehow, to date, I don't have many photos of the Seoul area. I do have a group shot as follows from a recent weekend and also a computer promotion I stumbled into not long ago.