Comparable to what?
I mean, just as one well known and google-able example, the Roman empire was obviously thoroughly heterogeneous. Maybe the key is that most people couldn't really travel? So no one from Lutetia ever really knew any woman from Alexandria for instance. Whereas today in Paris, obviously, a large number of people know people from Alexandria.
EDIT: I realize that if you were in the Roman Army, you were an exception to the general rule of people not knowing people from other parts of the empire. Obviously, Romans had to fight together against the barbarians. (Or rather, against the other future Romans.) But that would be an example of one of the few ways your average Joe in Marseille would get to know your average Joe in Leptis Magna.
But I digress. Most large, long lasting empires were not only enormous, but heterogeneous by necessity. Rome, China after warring states (even before actually), definitely Persia. In fact, I can't really think up any examples of contemporaneous homogeneous societies that could have even dreamed of competing with the historic behemoths.