Before the inland sea that now is there
There stood a place high in the air
And atop this northernly spire
The smithy's work vent forth it's fire
Illuin
It is said that Cuivienen in the Northeast of the world was the gulf of the inland sea of Helkar, that was made when Morgoth overthrew the lamps of the Valar. Since we are talking about the north, the good one is Illuin.
Illuin was one of the Two Lamps of the Valar, made by Aulë, filled by Varda and hallowed by Manwë in ancient days to bring light to the world.
Tolkien Gateway: Illuin