I think the Crushbone Citadel you're referring to is the top of the tower behind the throne in the ThroneRoom of Crushbone. In case you don't know where Crushbone is, it's at the north end of the Greater Faydark zone. It's a level 10-20 zone. And you can start grouping the Throne Room around 13 with good groups, but it's not hard to find many a player in there ready to take on the Mighty Crush. Emperor Crush and Ambassador Dvinn both spawn up in the tower behind the throne.
But anyway, I think the Citadel is the tower.