Overland Maps (like Crusader Kings, Civ, etc.) in Unity ?

For a long time now I've been banging my head against this question:

How to do map-centric games like Crusader Kings or Civ in Unity? I wonder why there's so little available in that direction. Assets are incredibly rare, it seems.

Obviously, at that scale you can't use mesh trees nor would you want to have large forests made out of tens of thousands of billboards. But no asset on the store offers world map scale forests of any kind. Nor do I see much in the way of world map scale terrain textures, etc.
Similar for villages, towns, bridges, etc. - very few assets at a world map scale.

Has anyone solved this problem and if so, how?

 

tens of thousands of billboards are fine. Use instances.

pretty sure the modern games in this genre use mesh trees, at least for near camera LODs.

The rest about map textures... it's not different than anything else. You can use splat map for terrain materials and use a 1:1 scale overlay texture as well. If map is really big, you may split into several chunks.

Just the standard techniques all over youtube will work. Only difference in this style is that because of camera angle, you can generally use lower resolutions

 

For something like Crusader Kings you could use this: https://assetstore.unity.com/packages/tools/game-toolkits/world-map-strategy-kit-2-150938

You can add plenty of trees or other meshes on that map if you implement LOD or Impostors (there's assets for both).

If it needs to be 3D like Civ there's several tile mesh assets, or just forcing things on a grid using a regular terrain would also work. Each grid tile is a 3D mesh and generally they are low-poly.

Take a very close look at Civ and you'll notice the detail either increases with camera distance and/or is cleverly disguised. Like here, those xmas trees are possibly just slightly scaled cones with a texture on them, and could be drawn with gpu instancing:


So just stick to mobile / low-poly assets. Of course any game faces the challenge of getting enough assets of the required kind with matching art style if you have to buy them all and kitbash them together.

Civ typically slows down over time due to calculating ever increasing AI strategies, tactics, pathfinding, combat simulation and the economy.