Question: What is this region highly contested between Poland and Lithuania called in Polish where Lithuanian Education Society Rytas is located? 
Sentence (from "Lithuanian Education Society Rytas"): The Lithuanian Education Society Rytas (Lithuanian: "Lietuvių švietimo draugija „Rytas“" ; "rytas" means "morning" or "dawn") was a Roman Catholic society fostering education in the Lithuanian language mostly in the Vilnius Region, then fiercely contested between Lithuania and the Second Polish Republic, now split between Lithuanian and Belarus.
Relevant evidence: Yes