Or maybe ask the current institutions (monasteries of various traditions) if things could be stored underneath them: they've managed to survive for a few hundre

Or maybe ask the current institutions (monasteries of various traditions) if things could be stored underneath them: they've managed to survive for a few hundred/thousand years already, and per the Lindy effect, [1] they may be more likely to survive longer. [1] https://en.wikipedia.org/wiki/Lindy_effect https://en.wikipedia.org/wiki/Lindy_effect