There's a CASTLE there.
Game of Thrones Season 7, Episode 1
The closest CASTLE to Hardhome
is Eastwatch-by-the-Sea.
Game of Thrones Season 7, Episode 1
You are not to leave the CASTLE walls
while we are gone. Do you understand?
Game of Thrones Season 1, Episode 8
I expect she's headed to Castle Black
where her brother serves as Lord Commander.
Game of Thrones Season 6, Episode 4
They can keep their Red Castle
Game of Thrones Season 1, Episode 10