This is exactly like Guess That Cosmere Character. But with places. Try not to go as big as a Shardworld or "all of Dayside!" for your place, though you can use hints like "it's on Threnody". Countries, cities, warcamps, towns, forests, mountains, anything like that is what you want to use.
Clue number one: We have currently never seen this place firsthand in a book.