vary resolution in different areas, Terrain Mesh?

Is it possible to vary mesh resolution of a single Terrain Mesh so that parts of it are high poly and other parts low?

The reason I’m asking is because I’m working on an environment which is visible from a height of say .5km where the topography is relatively flat and the player can’t get too close to the ground. That means that the horizon is very far away so I need a solution for modelling/texturing the middle/far ground while keeping it all in budget.

The gameplay area isn’t too large so I don’t need to load and unload cells; ideally I’d have a single mesh.

So the question is can I do this in Unity?
Can I model a single mesh in Maya/Zbrush and then convert it to a Terrain to paint up in Unity (to be more specific I mean a Terrain which will maintain the same vertices as the original mesh)?
If not are there shaders in Unity which support all the layers that Terrain Shaders seem to?
Can I model it and poly-paint it in ZBrush and import that into Unity?

I’m new to Unity so any help will be appreciated.

Thanks, Boris

I think you would use 2 meshes for this. If you can find the old Bootcamp demo, that’s what they did. Actually they used 2 Terrains (not meshes per-se). Or you can model one mesh in Maya that is exactly what you want but it would be a Mesh not a Terrain so you would not have the Terrain tools available for it. You would have to do it all in Maya I believe.