Pater's Vaetje is nice and easy to find, being right next to the cathedral (you can't miss it; big building, one spire not quite finished yet). It's in a typical 17th century Antwerp house and there are plenty of signs of its age inside. The floor is flagged with red tiles and the beams are visible in the high ceiling. The bar counter is a lovely carved wooden affair, with some attractive leaded glass work. At the rear is a small raised gallery. Continuing the use of traditional materials, the tables are marble-topped.
The beer list is pretty good, too. Obviously, the bottled beers are mostly Belgian, but I don't find that a great problem. The draught beers are rather boring and there is an obvious Alken-Maes tie of some kind.
Overall, a pleasant and intimate café well worth a visit. Really not bad for the centre of town.