@Oneironott 39 actually has an easy answer in the here and now; I want to see the Zorn museum in Mora, and take the night ferry to Helsinki.
Beyond that tho; I’d be curious to see what Mycenaean(ish) Crete was like. I’d wonder what Maastrichian Larimidia was like too, can you imagine all the biodiversity? Like there’d be birds, avialan dinosaurs, very reptilian looking dinosaurs, and all sorts of stuff that never fossilized.