Seoul, South Korea
I had never been to South Korea before, and I saw a good, cheap flight from Hanoi to Seoul, so I jumped on it.
Since I did little to no research ahead of time, it took a couple days to get into the groove and start to enjoy it fully. But, once I got the hang of things, like public transportation, restrictions on foreign credit cards and foreign navigation apps; I found Seoul quite enjoyable.
But, it is BIG. It is the 5th or 6th largest metro area in the world, so a week just wasn't enough to immerse myself.
Regardless, I enjoy getting my first experience with Korean travel in the big city. Maybe someday I will come back and enjoy the countryside.