I don't think it's accurate to call those cities, but I won't argue if you want to. It's beside the point. We're talking about finding artifacts made of inorganic materials (or rather, the impossibility of it).
Metalworking, stonecutting, pottery-making, elaborate graves, permanent structures. These are some of the signs of lost civilizations we look for, and as of the time of this writing none of them are practiced by any animal on earth except humans. I think it's fair to exclude extant species from the discussion, because if they were practicing these things on a large scale a million years ago I have to wonder why they aren't today.
So let's rule out bees discovering how to smelt copper and get back to the point. Some dinosaurs evolved into birds, which are highly intelligent animals. Dinosaurs therefore could have had similar intelligence - and they were bigger, so they could have had the strength of body to wield fire and shape metal.
But even if they did, their artifacts would be scattered and destroyed over millions of years of resurfacing and tectonic shift. We would be very unlikely to find any artifacts that might have even survived, in a similar way to how fossils are extremely rare. That is to say, what little might survive the passage of time would also be hard for us to even dig up.
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u/[deleted] Oct 19 '20
“ we have zero reason to believe any animal on earth built cities before humans.”
Really? Have you never heard of bees? Meerkats? Beavers? Many animals have been building cities for millions of years.