3d mesh : restrict H on volumes & surface ?

Hi,

I've been playing with 3d netgen mesher, is it possible to prescribe a local mesh size on surface and solid geometric entities ? For instance, as you can see on see attached picture, I'd like to refine the mesh everywhere but not in the ground which is fine enougth. If I increase the max mesh size, I'll get a coarser mesh everywhere. I know RestrictH and RestrictHLine can modify the size mesh on coordinated points and coordinates edges, but in my case, I'd like to prescribe the size (greater than the max size mesh) of a solid.

Thks.