Go to the Groenplaats and walk towards Rubens in the middle of the square till you stand in front of him and make eye contact. Next, make 90 degrees turn right and walk a few meters away from the statue. Now you’ll have to turn around 180 degrees to Rubens in profile. Now look closely at his thumb. After you've done this passers by probably think you're some kind of OCD retard but if you’ve found the right angle you will now see Rubens in full glory having boner.