Purchase a ticket and join the crowds at a game at Koenig Palast. If there's nothing scheduled while you're there, you might like to check if they give a guided tour of the grounds.
Located in Krefeld, this sporting facility is well worth including on your itinerary. But you'll find lots more to see in the area. Krefeld Zoo, Castle Linn, and Museum Haus Lange and Haus Esters aren't too far from Koenig Palast.
