Here's a video of a guy who builds a bridge between two scale mountains ... made out of real concrete with hand-twisted scale rebar, etc.
While it's an amazing effort, it's pretty clear that the project is more about the journey than the result. IMHO, he would have had an equally nice outcome just using plastic or wood and painting the surfaces with a scratchy concrete-like finish.
Two other notes:
- I loved his little scale shovel.
- If it was me, at around 6:45, the plastic mold would have been taken away only to reveal that air pockets had been molded in and the concrete towers resembled hole-filled gray logs of Swiss cheese. That's when you would have heard the screaming from the train room for which I'm famous...
Enjoy.
Steven J. Serenska