Which bizarre historical mystery do you most want to uncover the truth behind?

Looking for history rabbit holes to fall into.

For me it has always been the Bronze Age Collapse - how exactly did almost every major civilization near Greece and Egypt that was thriving in 1200 BCE just collapse or drastically weaken over a span of ~50 years? Related mystery - where did the Sea Peoples, raiders who are proposed to have played a role in the collapse, even come from?