When I asked an opinion about Antwerp to some friends, they all told me: very nice station.
And yes, Antwerp does have a very nice station, with multiple floors, spacious lanes and escalators, big clocks, an amazing steel roof and a beautiful façade.
Aside from that, the city is also interesting due to its mix of old and modern architecture. I think it has the smalles "grand place" that I saw in Belgium so far (very nice though, with the Brabo's statue in the middle) and many residential neighborhoods of more recent construction.
Very interesting are also the port (which is what historically made Antwerp great, together with the business of diamonds) and the riverside castle, optimally preserved for a building of the XIII century.