The Seoraksan National Park is located in the Northern East part of South Korea. It is a short 2-hour bus journey from Seoul to Sokcho. The Seoraksan National Park is one of the most beautiful natural site of the entire Korean Peninsula. Expect impressive rock formations, waterfalls and ancient Shilla-era temples. Seoraksan is the 3rd highest mountain in South Korea.
As the park covers over 400,000 km2, there many hiking path to explore. The Daecheongbong peak is the highest one. It stands at 1708m above sea level. It is a 22km return hike with a positive 1504m from the entrance of the park to the top of the Daecheongbong peak. It is an easy to medium difficulty hike. Only the last section is quite intense with a positive 1100m over 4.5km. To be honest, I thought that the first 2/3 where much more beautiful than the last third. If you do not fancy hiking this much, you will be more than satisfied with the easy section.
In my opinion, spending a day of hiking the Seoraksan National Park is more than enough. The city of Sokcho has absolutely zero interest.