I am trying to understand what natural resources a city would need access to in order to build walls/castles. I am trying to place my cities in relative location to all needed resources, but I need to know what all they would need to be near, naturally, to build.
For castles at least you need:
- Stone (so some sort of quarry)
- Wood (some sort of hard wood such as oak)
- Solid ground to build on (I built another one... that fell over and then sank into the swamp.)
As far as construction techniques, whatever you want, scaffolding and pulley systems both fit the medieval theme.
You need anything that does not compress or warp under pressure. You need stuff that either holds, or breaks. If it breaks you know you have used to little of it; add more.
This leaves you list with things like...
Stone Concrete/cement Metal
...and that is about it. Add to that the metal is a very precious resource in those ties so you are left with stone and concrete/cement.