3 ms·

The locations of rivers, good natural harbors and resources would have been completely different tens of millions of years ago.

• dontbenebby 7y ago
  That's a good point, I just meant that it seems odd to focus on cities. (Especially since while the cities themselves are small, the swathes of land to supply them aren't. Also I think someone else commented evidence of atomic tests would persist a very long time, for example?)
• dredmorbius 7y ago
  Different, yes. Unknowable, no. We know the general distribution of continents dating to 550 million years ago (Gondwanaland), and to some extent prior, though that largely predates the Cambrian explosion of complex life on Earth. Ancient coastlines, estuaries, and riverbeds leave quite distinctive geological traces and would be detectable. We'd be looking for ancient civilisations on or near such features.