Antwerp
I went to Antwerp for one night last week and here are my recommendations
Old
The Museum Mayer van den Bergh is a 17th century building filled with a 19th century collection of some of the best paintings I have ever seen, including the Breughel 'Mad Meg' apocalypse pictured above.
The Kerry James Marshall retrospective at Muhka - the reason I went - was amazing and his more recent paintings are an incredible development in technique, medium, scale and content. Tim van Laere is a contemporary space with some good people in its roster.
Every single high low medium clothing shop in Europe has a space in Antwerp. Highlights for theatrical shopping experiences are Seven Rooms (I have never seen a concept shop like it), Dries van Noten and Delvaux.
Sustenance
Fiskebar - order the mixed grill (or if you like squid, expect a shoal when ordering the calamares) and make sure you book. The ginger tea and Aperol Spritz at cafe/bar Vitrin across the road is also very good. I also ate lunch every day at healthy veggie Lombardia which was bloody tasty.