Apparently so. From the first moment I saw the picture I could see it wasn't just a wall. I don't understand how anyone was fooled by it, but I guess it's similar to the dress where some people just see it one way.
I saw this somewhere else, labelled as an optical illusion. I saw it straight away, so assumed the illusion was what I thought I was seeing wasn't really there, but it is, and it seems so obvious to me that I can't see how anyone would be fooled. Weird.