Well, oldest still actively used for scientific research. The folks who built Stonehenge might have a better claim to oldest, with Gobekli Tepe TBD.
Question: If AI controlled drone ships arrived here thens of thousands, maybe even millions of years ago, and those ships carried the DNA and instructions of their source civilizations and their AI robots introduced that DNA into the local fauna to create hybrids capable of surviving on out planet - are they really aliens at this point?
Asking for a friend named GLrxbLyx.
A Vatican observatory, what on oxymoron. What do they need an observatory for, after they burned Giordano Bruno at the stake? And lucky for Gaileo they only sent him home and didn’t allow him to go out.