started with a very low poly shape of a watch tower I tried to model in my first year of using blender
uv mapped it
put a free brick texture from ambientcg + adaptive subdivision + displacement of geometry
Use ambient occlusion node along with hidden geometry to darken some areas of the texture, bake that result to its own image texture file.
Some free vdb volume objects from embergen’s website.
Some free plants: https://blendermarket.com/products/the-plant-library
Nishita sky texture and 2 sun lamps.
Lots of begging for help on blenderartists.org in between each step: How to bake when UV's are far out of bounds?