It looks like a door opening in a concrete wall, right? It's not. This is a flat mirror designed by Sarah Dayo that creates that optical illusion. She writes:
Sometimes we cannot help but to try and catch a glimpse of the otherside.
Passing through the everyday spaces we inhibit, the door half opened always stirs up a sense of seduction and curiosity within us. Inspired by these ordinary yet inexplicable moments in our daily lives, I designed a mirror that gives an illusion of a door opening on any given surface.
Link via Make | Photo: Sarah Dayo
Perhaps, it will be better if the triangle was touching the vertical line of the concrete wall.
P.S.
And a windows opening ?