Countryside from Seoul

I am traveling to South Korea in September to Visit my sister who is teaching english. I will be staying in Seoul with my Dad as well as in Siheung. I am wanting to get out to the countryside and possible do some hiking, and explore the natural beauty of Korea.

I am looking for some ideas of where to go to get out of the city for day trips.
Also wondering the best way to get to these places, busses, tours, ect.

Thanks!

If you only want to do day trips, it limits your range, but you could head to Sokcho for Seoraksan National Park. It would be a very long day, but it's doable. In Seoul, there are frequent buses to Sokcho from Gangnam Express Bus Terminal and Dong Seoul Bus Terminal. Once in Sokcho you can catch city bus #7 or #7-1 which are very frequent (every 10 minutes or so I think) which take you to the main central area of the park where you can do several hikes.
A closer trip would be to head to Wonju for Chiaksan National Park which is supposed to be really nice also, but I haven't made it there yet. The same 2 bus terminals in Seoul I mentioned above have frequent buses to Wonju, and then you can catch a city bus to the park.

Jason

Many Mountains in Seoul...
Or you can conveniently use subways to get around Gyunggi Province which is the closest provicne to Seoul.
Nothern parts of Gyunggi Province are more scenic, i think..
DMZ trip with Haeiri trip, or Namyangju Domulmury..(you can use central line)