https://www.bloomberg.com/news/features/2021-04-27/inside-architecture-s-wildest-conspiracy-theory

https://skeptoid.com/episodes/4765
The overall premise is an alternative history. A vast, technologically advanced “Tartarian” empire, emanating from north-central Asia or thereabouts, either influenced or built vast cities and infrastructure all over the world. (Tartaria, or Tartary, though never a coherent empire, was indeed a general term for north-central Asia.) Either via a sudden cataclysm or a steady antagonistic decline — and perhaps as recently as 100 years ago — Tartaria fell. Its great buildings were buried, and its history was erased. After this “great reset,” the few surviving examples of Tartarian architecture were falsely recast as the work of contemporary builders who could never have executed buildings of such grace and beauty, and subjected them to clumsy alterations.
https://www.youtube.com/channel/UCHh5VLgqo4XPWVDO-NEQmpg/videos