Earlier today my friend and I dropped by 융정다원 (YongJangDaWon) My pal grew up in Nampodong so he knows the area very well and tells me this teahouse has been around for quite a long time.
The easiest way to get there is to take the escalator up to Nampo tower. One flight up only on the escalator and you should see an enterance to a temple on your left. On your right is 용정다원 or dragon 용, 정pavilion 다tea 원 place or in this case according to the chinese characters garden. Apparently 차isn't the only character for tea. On the window you'll notice right away that they serve various coffees and smoothies now.  Go the distance! Their teas are amazing, if you know what to order, and I am at your service!
They are well known for serving Korean teas in the very traditional old Chosun dynasty style goblets and tea bowls.
I recommend their 오미자차 (OMeJaCha) or 5 flavors tea. It seriously actually has 5 flavours all in one sip: sour, sweet a tad salty and fruity are as far as I can discern. A wonderful fruity complexity indeed. The lady there informed us that she picks the fruit herself. Omejacha, you can't go wrong!  They are open 7 days a week too! Feel free to drop by anytime. And do make sure you go to the 2nd floor!!! (Way more character there).