>>2795474i would skip Gyeongju, it's far and there is too much to do in seoul anyway
take a day trip to Suwon and see the fortress & market there
For nature visit Bukhansan if you enjoy hiking, or rent a bike and ride along the Han river from around Guri Hangang Park all the way to Yangpyeong. Seoul has very extensive bike trails, every river has bike paths along it.
Another beautiful bike trail is the path from Gajwa station up the river. stop at Hongjecheon Artificial Falls, see Cafe Pokpo which is all over IG, climb Ansan park & see the Yeonhui Forest Rest Area, then keep going all the way up to Okcheonam Buddhist temple.
persoanlly i enjoy hiking more than biking, i would just go to Bukhansan or hike Gwanaksan if you're in southern seoul.
>>2795481seoul is hot and humid as fuck in summer. Jeju is cooler with the sea breeze
>>2795513hiking is the national pasttime for old people
>>2795691you won't have the full korean experience unless you go with someone familiar with korea who speaks korean. all the actual fun/enjoyable experiences in korea are only advertised to koreans on naver and not tourists, they only advertise the lame shit to tourists, so if you look online all you'll see is the lame tourist shit.
the best part of korea is going to one of the infinite cafes, pop up experiences, enjoying the food, the convenience of delivery and high quality inexpensive services; but as a non-korean you will never experience any of this and will not have a great time.
These keep changing all the time and i do not live in korea any more so the places i know are outdated.
A genuine answer for you: find a KOREAN GIRL and take her on a DATE to lotte world. And rent high school uniforms and dress up. it's a very popular kind of date. It's only $30 per person when you use the promo codes online (have the korean girl book this for you). Then eat at lotte world mall after.
If you like league of legends then check out LoL Park in Jongno