Location 2 is a razor wire tunnel. According to the book, "it stretches across empty air, with a thirteen-hundred-foot drop to the city below. The tunnel is made of curling razorwire with occasional iron supports."

This is probably much easier in vector than in raster art. The supports are just some simple grey lines, drawn to an isometric perspective. These probably should be a bit less regular and symmetric, but whatever. I found a free razor wire brush by killersevendesigns on deviantArt, so the wire is just some loops (again, keeping to the perspective) with that brush.