Derinkuyu is the largest excavated underground city, which could house over 20,000 people

" what'd you find? Another bone or a pot? "
" uh... No... No I don't think so "

funnily enough, it was found behind an old man's wall when he was renovating

Agreed, that's probably the worst case of knowledge being lost in human history.

I remembered reading something about how Alexandria didn't actually have much that wasn't already copied and stored elsewhere.

Idk... the works of Hero alone are enough... I mean... that fucker built a steam engine and a wind turbine.... and that's what survived.... who knows what else he came up with.

also Aristarchus of Samos.... who proved the Earth orbited the sun 1700 years before Copernicus, although Yajnavalkya beat even Aristarchus by nearly 500 years.