First place we stopped in was Delirium Café as my girlfriend had been here on a previous visit. It was early afternoon and the place was not busy at all. The barman was friendlier the second time I went to the bar as I brought my empty glasses with me.We tried several different beers, but I could not see how there was supposed to be "thousands". Mind you we were in the downstairs bar, so I can't vouch for what was upstairs.
It was quite hard to find as it's down a tiny little alley, but I probably would have went back had we not found the much nicer "Little Delirium" on Rue du Marche Aux Fromages later that evening, which I assume is owned by the same people. We spent some time in Little Delirium each of the four days we were in Brussels, and sampled pretty much every beer on the menu (I'm Irish, she's Finnish :D). My particular favourite was Delirium Nocturnum, but every beer we had was tasty, and several wer quite strong, 9-10%. They do a three beer taster for €6
This place had a really nice atmosphere and was much cleaner and modern than Delirium Café, staff were really friendly, and they played a quite varied and eclectic selection of music.
All my ratings below are for Little Delirium, as I can not find a seperate listing.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.