Danish Bus Optical Illusion

Yes, today’s picture shouldn’t be considered true optical illusion. No-one normal would be deceived seeing this huge snake painted on public transportation. Your brain would simply prevent it from fooling you. However, I think it’s great example of creative advertising. Not only did it catch my attention, it became viral around the net as well. The only thing I’m not certian about, is what should this billboard represent? Somwhere in back of my head quiet voice suggests how this ad’s purpose was to promote public Zoo of some sort, but I can’t give any guarantees.