I used to go to Seoul every year for winter break throughout college. My parents lived in China and we used Seoul as a meeting point. I also got to spend time with my entire family on my mom's side, all of whom still live in Korea.
The last time that I went to Seoul, which was two years ago in January 2013, I had just graduated from college. I was glad to finally return to Korea, and this was the first time that I didn't stay with my family. It was nice to play tourist in a city that I knew so well with a new travel partner and a fresh perspective.
Mattia and I stayed in Hongdae, a young neighborhood known for its cafes, shopping, and parties. We definitely made the best choice--we had so much fun buying and drinking and going out and eating and sipping coffee.
One of my favorite parts of Seoul is that there is an immense coffee culture, and a particular cafe culture. It's hard to go one block without running into 5 different coffee shops, each ready with an extensive menu and free wifi.
Mattia and I only had a few days before he had to return to Shanghai to take a few exams (he was taking a semester abroad there) and before I had to meet my parents, who were coming from China. We went to most major neighborhoods in Seoul and feasted on all the popular Korean dishes (plus soju, of course).We even made a trip out to the DMZ, which was a first for me as well. I did my best to teach him about Korean culture (he even watched My Sassy Girl with me!), though I think he just enjoyed the Korean barbecue and the cafes with free wifi the best.
I hope you all get a chance to visit South Korea. Seoul is such a fun, vibrant city with amazing food that literally never sleeps. You can find 24-hour everything, from bath houses to shopping malls to coffee shops to PC rooms to restaurants and karaoke.