A weaver bird nest. More like a hive. Or maybe not, biologically speaking. But the whole underside is riddled with nest holes. I never got an exact figure as to how many weaver bird families might live in one nest, but my observations wouldn't put 50 out of the question. The adaptive beauty of it is that if I'm a predator, say a snake or something, and I get up on top of the thing and try to make my way down in to a nest opening, I fall off. It's brilliant.