The mystery city where Waldoniel was

OK, busy and little Internet, but back nevertheless.  The trick today is to guess what city in Austria I was.  But to make it more interesting you can only win if you can say why you think that city is the city you claim to be.  Two ways to reach that conclusion: either you name the building or you guess where it was featured.  That is, two possible first prizes here though naming the building sorts of gives you the real first prize.