
A raven came from the Citadel.
Game of Thrones Season 6, Episode 10

but everyone in the Citadel,
Game of Thrones Season 7, Episode 1

is not being immediately
expelled from the Citadel.
Game of Thrones Season 7, Episode 3

The Citadel isn't Castle Black.
Game of Thrones Season 6, Episode 3

the Citadel to give him back his chain.
Game of Thrones Season 3, Episode 7