The St Peter's Abbey is these days an Art Center with temporary exhibitions.  If interested in history, the Alison Movie Guide will take you on a trip through it's rich past.  The refectory wing with it's painted and restored ceiling is a must.  An orchard with a vineyard between the abbey and the river Scheldt is truly a hidden gem (and can be visited without entering the abbey). 

St Peter's Abbey

 St Peter's Abbey (Official site)