Can I do a day trip to Mt. Sorak?
Also feasible. Journey by Express bus to Sokcho city where Mt. Seorak is located takes about 2 hours and 30 minutes. If you take the earliest bus around 6 AM you’ll arrive there with plenty of time to take the cable car at Mt. Seorak, explore around and then take the express bus back to Seoul.
However if you plan to do hiking, it is better to stay overnight there.