I'd like to spend some time distilling this into how we can very declaratively specify world/chunk generation.

Ad-hoc Structures, dungeons & landscapes come to mind

I think this could ideally use the same functions as block.clj for defining things like dungeons - But that might not be suited for landscape generation.. perhaps looking at using clisk for chunk generators? It has a way of defining 4D texture maps which could possibly be mapped to block types?