On our way home from a weekend in Antwerp, we stopped off for some sight seeing and lunch at Westmalle. As it is only about 20km East of Antwerp, it was well worth the time to get there. Plus, we were able to knock off another Trappist abbey (Orval, Westvleteren and now Westmalle).
The cafe is open 7 days a week from 9am to midnight which is good to know. The abbey itself was not really open for tours but the grounds of the abbey were huge and they let you walk all over the place.