I'm working on a fountain made of cobblestone. The base is currently a single object. You can see the the base in full here:
(ignore the clipping of the texture for now, I'm still working on the UV map).
What I'm trying to do now is make the texture pattern on the top of the base to follow the ones on the side, so it seems like it's actually made out of cobblestone bricks. If you move the fountain around a bit, you can see that by coincidence the bricks match up, but it makes clear what I mean: 
How would you do such a thing? It would be really helpful, thanks! If it matters, I'm using cycles render.

Also what do you mean by concentric? I presume that you mean to project the stones around a centered axis on the texture?
– user125756 Aug 26 '18 at 09:26