That's Moat Cailin.
Game of Thrones Season 5, Episode 3
Gather whatever men you can
and ride for Moat Cailin.
Game of Thrones Season 4, Episode 2
They're encamped at Moat
Cailin as we speak.
Game of Thrones Season 6, Episode 5
The Starks will have dominion
over all lands north of Moat Cailin,
Game of Thrones Season 2, Episode 5
May our happiness spread from Moat Cailin
to the Last Hearth.
Game of Thrones Season 5, Episode 5