>>212487798 (OP)Anywhere in the mainland except Athens and maybe Thessaloniki has no tourists.
The eastern and northern Aegean islands like Lesbos, Chios, Thasos and Lemnos hardly have any tourists.
Many of the Dodecanese like Kalymnos, Leros and Karpathos same.
There's some obscure islands like Kastelorizo, Agios Efstratios, Oinouses, Gavdos and many others that you have to be really adventurous to visit.