I feel the same, but I did stop short of directly claiming it. I'm wondering if in 60my, they might only have an infinitesimal trace, or get subducted or someth

I feel the same, but I did stop short of directly claiming it. I'm wondering if in 60my, they might only have an infinitesimal trace, or get subducted or something. I still feel like the major cities can't all be in erosive environments or liable to get their crust recycled, or whatever other processes can fully annihilate them, but I don't know quite enough about geology to be confident over tectonic timescales. Scifi side note: imagine a world so thoroughly altered that even the magma from subducted crust shows signs of civilization.