Noticing the Unnoticed

My workmate, GC, showed me this interesting link today:
http://www.publicartaroundtheworld.com/Impossible_Triangle_Sculpture.html

For a few moment, I couldn't even recognize the place, although I have actually passed through that round-about with the sculpture many many times.
Well, apparently there's an intelligent idea behind this sculpture, rather than just a random steel shape *doh* Quoted from the website above:
"the trick or illusion of this clever design is that if you wander around it long enough you will find a spot where the sculpture will give the illusion of being a perfect triangle."

Now I can't wait to get back to Perth and wander around it to find the perfect triangle..let's just hope I don't have to spend one whole day to figure it out. If I'm in good mood, I might post my finding here later.