Landscape
Inspired by this water effect and ending up looking very similar to this design I sliced a 3D model of a landscape using 123D make and then basically redrew everything in inkscape once I had that basic shape (for some reason 123D make decided to round off the corners of my cube post slicing). It's cut in 3mm laser ply and 3mm blue tinted perspex. As each layer of perspex is added the colour deepens and you get this nice depth effect.