Todays Jewish Antwerp (or Antwerpen) is dominated by two interconnected distinct features: its large Orthodox and Chareidi communities and its famous Diamond Quarter.
Diamond cutting, polishing and sale has traditionally been a jewish business with strong involvement of Chareidi community.
Interestingly, there are no kosher hotels in Antwerp although some of those located in or near the Jewish Quarter will serve some sort of kosher meals (mostly breakfast and you can expect chalav and pat yisroel).
Anyway, consult www.jewishtraveladvisor.com before you travel as the hotels may be changing their policies over time.
There is a number of kosher restaurants in Antwerp (Hoffy's my favourite) with strong hechshers of the Machsike Hadass sort and overall atmosphere is pleasant even for those used to Brooklyn/Israel/Golders Green kind of heimishe yidishkeit.
Check www.bh.org.il/communities/Archive/Antwerp.asp for information on Jewish history in this city and en.wikipedia.org/wiki/Jewish_Community_of_Antwerp for practical information.