Mt.Seorak is known as the most beautiful national park in S.Korea!
It is the highest in the Taebaeksannmaek Mountain Range and designated a UNESCO Biosphere Reserve. This is a place that you can definitely find lots of outdoor activities and beauty of the park!
There're also a lot of wild life ,too

Kwonkeumseong fortress - Cable car included in the tour

Shinheungsa buddhist temple is located in the park, easy access

Hiking is optional but there are two course which is easy
1. Biryeong water fall course - round trip 3h
Harder than biseondae course, quite many uphill and stari case

2. Biseongdae rock course - round trip 2h
beatufil scenery along the way, it's really easy

3. Full day hiking to the peak , Daecheongbong course
Very healthy , super early in the morning starts hiking and finish at late afternoon, 8 - 13hours
otherwise, mostly people need two days

Tour guide will meet you at your hotel in Seoul
Departing pretty early to get in the park earlier