Should I Use A Terrain For A City?

Hi,
I'm new to Unity and I'm trying to build small semi-open city.
The city has some natural parts, like grass, a small park alley, hills(with buildings on top) and there is a forest and a river outside of the city.
I can't figure out, if I should use one big terrain - but then a lot of terrain parts will be under roads and buildings, damaging optimisation.
- or several small terrains, seems like the most logical, but I'm not sure how many terrains I can use with Unity without breaking a system
or not to use terrain at all - river, hills and park alley soil will be replaced with concrete. It will make city look more industrial and perhaps more scary, which is good for my horror game.
I would love to hear you responses!!!

I also own Gaia, but I don't think it can help with the dilemma.
Edit: I also own infiniGRASS, which is supposed to help to create grass on any surface, so I thought, if I should make soil and natural parts using 3d models, rather than Unity's terrain.

P.S.: I hope, I'm using the right subforum.

 

CityGen3D environments use Unity Terrains as their base. This gives you LOD and all the other features you get from the terrain system, which has improved considerably over last year or so.

It also makes it really easy to transition between urban and natural environment, which it sounds like you want to do.
The amount of terrains you need really depends on the size of your environment and how high resolution you need the terrain to be, because each terrain has a maximum resolution so the bigger it is the more this is stretched out.

If you are still in two minds about the design of the environment, its probably easier to protype ideas using the terrain system anyway, then make a final decision once you've narrowed down the ideas a bit more.

Hope that helps, but there's not necessarily a right or wrong way, you'll perhaps only know what's right for your project after trying a few things out. You dont necessarily have to get it right first time (unless you have really tight deadline!)