We only had a drink in this café, but it was very nice. It is located near the Opera House in a quiet area and we discovered it accidently when we went back to our car.
We were the only guests, service was not so good, and it was also very expensive. But I liked the interior and the general atmosphere.
I was also very happy to discover a vegan salad in the menu that was explicitly marked as vegan - I had not seen the entry on HappyCow before! A pity that I was not hungry :-( The salad sounds very good, though, and if I go to Halle again I will definitely give it a try.
Cons: Expensive, Slow service although only customer