The installation window - 'instalraam' in Dutch - in Onderstraat is a permanent 24/7 public exhibition space. Usually it is used by one artist for a few months. Onderstraat being a street in the historic city centre, it attracts visitors and suprises unsuspecting wanderers and tourists.
The word 'instalraam' is a contraction of "installatie" and "uitstalraam" i.e. shop window. No way to translate this into one word in english, we're afraid.