Game of Thrones debuted 13 years ago and HBO continues to spin off spin-offs, the most notable being Dragon Houseand the next A Knight of the Seven Kingdoms series. Now, George RR Martin, the novelist who created this fantasy world, has shared some details about an abandoned Game of Thrones spin-off that he would like to revisit.

On his blogMartin wrote about his recent trip to Amsterdam and how the country inspired his fictional country, Braavos, in the Song of Ice and Fire novels. Martin then casually dropped the reveal of the potential show on Braavos.

“One of these days I’ll have to write that Braavos story that we were developing for HBO,” Martin noted. “They shelved this one a few years ago, alas, but that doesn’t mean I won’t return to it…once Winds of Winter is finished, of course.”

In Game of Thrones, Braavos is the home of the Faceless Men who trained Arya Stark to become an assassin and master of disguise. She spent a long time there before returning to Westeros for revenge. But there’s still a lot to learn about Braavos in possible prequels or sequels.

As for The Winds of Winter, it is the sixth novel in Martin’s story which inspired the television series Game of Thrones. Martin has been working on it since at least 2011, but the book still doesn’t have a release date in sight.