Unemployment rate plotted against inflation for 8 countries over 10 years. Every layer represents a year and each country is a wire of a different color. This physical visualization was built by Tim Dwyer for his PhD dissertation. His goal was to experimentally compare a 3D and a 2D data representation, and he used a physical object to emulate a perfect 3D display.
Source: Tim Dwyer (2005) Two and a Half Dimensional Visualisation of Relational Networks. PhD Dissertation.