Stacked Walkways
A pretty neat demo of two walkways on top of each other. The technique uses scenery items to fake the look of the walkway, so you don't look like you're floating... it seems pretty clear that with a little bit of artistry, the proper scenery items could be created to make the upper walkway look nearly flawless. Also contains an intriguing extension of the author's untextured wall experiments.
Levels in map "Stacked Walkways":
stacked walkways
Levels in map "Untextured Walkway":
untextured walkway