How this Unwrapped Cube was done?

Hello Blenders

Here’s a link with the file that I am struggling to discover how the view of this cube was made. I worked with this file doing the unwrapped texture but some 3D options escape of my knowledge.

I hope some readers would be kind to tell me where is this tricky option that I can’t find.

80 mb file
https://docs.google.com/file/d/0B91VrhY5rCpNb0F0Q2trWEd6eHM/edit?usp=drive_web

Thanks in advance.