Michael Jennings has a nice photo essay about the new viaduct in France:

The materials from which this bridge has been built are vastly stronger than anything that existed even 20 years ago. I have said this before, but this is in my mind the defining characteristic of modern post materials revolution structural engineering. Structures are then, flimsy. They almost look like spider webs. The defining characteristic of industrial age engineering was bulk. But now we are in this virtuous circle of stronger and lighter materials allowing a much thinner deck, allowing the other parts of the bridge to be lighter and less substantial too, allowing still more economies elsewhere, and a rapidly dropping cost of projects like this.

That will be a characteristic of a space elevator as well, if it’s built.