Gao Den is an affair of the heart for me and even though it is quite on the outskirts I never regret going there. Also I am not afraid to say that you cannot find a better Vietnamese restaurant in Prague! It is a family-owned restaurant focusing on modern Vietnamese cuisine opened by two brothers with Vietnamese roots. I don’t know much about original Vietnamese cuisine, but even if it wasn’t authentic, which I doubt, it is just too good.
If I can make a suggestion, come around lunch time as the prices are pretty good for what you get at this time especially. You can choose from the daily menu which always includes a few main dishes, soups and Vietnamese baguette Banh Mi. And if you can’t make it for lunch, it is worth paying a bit more and choosing something from their permanent menu. If you are indecisive like me, go for their Pho! Always a good choice.
I can imagine that it is not the most attractive area to go when coming to Prague as a visitor, however if you happen to be around by any chance, just go and enjoy the porn food or the other way around. Also, I heard some rumors that they are planning to open another Gao Den in Anděl district. I secretly hope the rumors come true!