In terms of top places that I would hang around in Seoul, I have developed a list of the popular areas that I generally visit.
Gangnam is a pretty expensive area because there are a lot of high-end shopping areas, as well as bars. I’d consider this a pretty fancy area. And in terms of clubbing and having a long night out, this area is predominantly Korean, so you will not find many foreigners. In fact, bouncers will likely not let you inside if you are a foreigner. Most of my Korean friends and clubbers, they say that you will be more likely to be turned away from entry.
Sinchon is a nice area to hang around especially since it is close to Yonsei University, this means that there are a good number of students and college culture. This is a fun area to hang out because you can watch a lot of street performances and visit some good, affordable restaurants. It is nearby Ansan mountain so you can take a climb too!
Hongdae is the hip area of Seoul. There are a lot of students congregating in this area because there are a lot of high schools and universities nearby, particularly Hongik University. This is one of the best places to go drinking or clubbing because there are always a lot of young people. Every night, there’s a party. This area also has a lot of restaurants that are open in the dead of night. You can also catch a bunch of street performances here as well!
Itaewon is the foreigner area of Seoul. It is a very popular hotspot for foreigners and you can find a lot of good supermarkets and restaurants for foreign cuisine and products. Also, this is a popular place for clubbing as well and it is generally more foreigner friendly!
Yeouido is a nice park area by the Han river. It is fun to visit here because they have street vendors and nice public areas for cooling down in the summer heat. Honestly, all along the Han river is very nice and I highly recommend biking the Han river!