@ned aliens! where? they left some machined granite!
humans made these. how? idk
my faith limits such possibilities, but here are 2.
1. pre-flood.1600 years of genius's making stuff. but how did these survive? did noah carry them? did they survive underground and Egyptians found it?
2. post-flood. humans still smart. made precision machines - perhaps in metal. metal since corroded or recycled. perhaps knowledge lost after Babel?