Seorakasan is another national park - it's over near Sokcho, up towards North Korea. It's actually over the 38th parallel, I believe - it's that weird little piece of the border that juts northward.

If you want to do hiking or anything, we found that the crowds of Koreans diminished the longer the hike was - if you do the 3km walk to the tottering rocks, for example, there will be tons of Koreans and gift shops. If you head out on day-long hikes, you'll find the solitude you are craving.

Kumgang is an expensive option for a mountain retreat...