Stedelijk Museum voor Volkskunde (Folk Museum)
Unless your passion is everyday life in 19th-century Flanders, don't bother with this. The exterior is interesting enough (it's the almshouse of the Shoemakers' guild), but the interior is very predictable

St Salvators-kathedral (St Salvator's Cathedral)
Despite a few pretty tapestries, this is an unimpressive building. The original cathedral was burnt down by the French at the end of the 18th century and the opportunity to build something new and equally imposing was overlooked.