James said it was a GoT location. Green Glass Sea for anyone wondering is the first atomic bomb test site located in Nevada in the U.S. (Yes, the U.S. has bombed their own soil. Multiple times too.)
Because ofc guessing for something game of thrones related seems better than to guess for something within a children’s book.
^ Also said children's book is historical fiction as well, as it is based on real locations and real people and real happenings. I read it as a child and it was good.