Good point. Aren't their labs, what, completely underground? Black Mesa had some surface to it.
Hopefully you know that's not what I meant. I was referring to, specifically, a presentation going on in a side room showing how Black Mesa was owning Aperture in terms of profits.
But anyway, yes, Aperture is (from what we can tell) all underground.
Black Mesa is probably bigger, not including the empty spaces of Aperture.