Things To Do
Korean River (Hangang) Parks
Korean River (Hangang) is smack in the middle of Seoul, and there are many beautiful parks in front of the river for people to relax, eat, bike and all that (crush beers at night). I love going to these parks when the weather is nice. There are bikes, picnic mats, lawn chairs that you can rent for extremely cheap. Korean people love to make instant ramen at nearby convenience stores and eat it by the river (almost a national pastime). I definitely recommend two river parks (Yeouido Hangang Park, Banpo Hangang Park). FYI, Yeouido is the financial hub of Korea - while Banpo Hangang Park is a rich, residential neighborhood.
Gyeongbokgung Palace
Gyeongbokgung Palace is the largest and most important royal palace in Korea. I have been there a few times, and personally think its pretty sick. Definitely worth at least going once. Only $2 entry fee (KRW 3,000 per person).
Itaewon Station
One of the biggest nightlife hubs in Seoul. There used to be a US military base in Itaewon, so its got a lot of American influence and is the most international part of Korea. There are a lot of restaurants, bars, clubs. Great place to bar hop, and also go out (techno, house, hip-hop, trans/gay clubs).
Apgujeong Rodeo Station
Another major nightlife hub in Korea. Apgujeong Rodeo (Gangnam) is one of the richest neighborhoods in Korea, so it feels a bit more classy (Itaewon is more trashy). There are a lot of great restaurants, and also a lot of boutique clubs here with great music.
Hongdae Station (Hongik University Station)
Another major nightlife hub in Korea. By land area, Hongdae probably has the biggest nightlife. This area is just huge. This area rose to popularity due to its location (being close to college campuses) so the crowd is definitely much younger (low to mid 20s). I personally don't go anymore because it makes me feel old as hell.
Seongsu Station
The hottest neighborhood right now for foreigners due to vibey restaurants, cool stores (luxury Korean brands, designer brands, multiple pop-up stores), Korean bakeries and etc. Not a nightlife area, but worth a visit in the day to see how Koreans live. Definitely more gurl-coded.
Myeongdong Station
Myeongdong is a very traditional neighborhood for Korea's tourism (shopping, street foods, hotels) so you will see a lot of foreigners. I wouldn't put this at the top of my list, but worth checking out if your hotel/Airbnb is in this neighborhood.