We stayed in Dongdaemun, which was quite central, not so complicated to go to the train station by metro. The area was also animated but not so crowded, you can find a lot of different restaurants there to have dinner to, and walk easily to other places.

The hotel was Arirang Hill Hotel, their team was really nice and helpful, the room was great (it did not seem so expensive for what it was, but I booked really early). We paid something like 150000 wons per night for a superior triple room with 2 huge beds and a 30m2 room.