If you are in Seoul, Korea and you are looking for a musical instrument, chances are you will find what you want at Nakwon Arcade (낙원악기상가). They have shops for guitars, ukulele, drums, amps, piano, flute and all manner of instruments.
The nearest train station is Jongno-3ga (Line 1, 3 and 5). Make your way towards Line 5, exit 5. Take the stairs (not the escalator) out of the station. Once you are on ground level, you can see a smaller alley slightly off to your right. Cross the road and walk down that alley. You don’t have to walk to far in you will see a few flights of stairs leading up to an enterance to a building. That’s the one you want. Check this map, it may help.
Personally, I got a ukulele at 100,000 won. The shop threw in a padded gig bag, a tuner and extra strings. It was an okay deal. A word of caution, if you are a foreigner and don’t know how to pick a good (insert instrument here), you are better off not buying anything from Nakwon Arcade. Most of their items are not price tagged and you have to ask them for the price. When I was shopping around the prices they quoted me was on the high set of things. I have a feeling a Korean would be getting different quotes for the instruments than me. In the end what I did was to give them my budget and have them work around it but at the same time you must know how to check the instrument you are buying to make sure you are not being ripped off. Regardless it is an interesting place to visit if you play an instruments.