I wasn’t even aware that there was a conspiracy theory about it. I’ll spend a few minutes checking out the history and whatever the conspiracy is supposed to be, though.
Most of what I learned about architecture came from a undergraduate elective I took on Medieval and Renaissance Art. It was a really good course taught by a woman who’d show slides, many about the art and architecture of Italy, and by the time she finished talking you’d appreciate what she was explaining much better.
I wasn't aware of it either, but I figured something was up, because there was no such empire. The Tatars/Tartars were Turkish Islamic thugs that were eventually beaten by Ivan the Terrible =-- but they are unrelated to, for example, the Tartaria Tablets, which remain undeciphered, and appear to be in the same tradition (in some fashion) with the runic systems formerly in use (and sometimes similarly undeciphered) from the Aegean and points north, and actually found among the cave paintings (those are generally one or two characters, and probably if they ever had a meaning, it was lost 15,000 years ago).