In Tolkien's Middle-Earth, an enourmous bay cutting deep into the northern shores.
An observation of the topography of this region, as depicted on various maps originally made in the late Third Age, suggests that at some time in the remote past the Sea broke through the land which then lay to the north of the Blue Mountains, and flooded far into the wastes of Forodwaith. If so, then such a dramatic change in the shape of the lands may well be connected with the destruction of Morgoth the Enemy at the end of the First Age -- which is known to have had catastrophic consequences for that region. For the Great Battle in which Morgoth was overthrown by the Valar themselves unleashed titanic forces which not only olbiterated his evil fortress of Thangorodrim, but also inundated Beleriand, the land of the Elves in the West of Middle-Earth. Even the Dwarf-cities of the Blue Mountains were destroyed in the cataclysm.
Is it therefore unreasonable to assume that, during the lat Third Age, the waters of this icy bay lay over what had once been Morgoth's ancient realm of Angband? His chief fortress of Thangorodrim is known to have been located in the Far North, and the icy colds of that region (which still lingered in the Third Age) were said to be an inheritance from his evil realm. And since Beleriand and Númenor were both drowned as a result of great wickedness, once may reasonably speculate that the first evil realm of Middle-Earth was also plunged under the cleansing Sea.
Note: on all currently available maps of Middle-Earth, the name of the Ice Bay of Forochel is placed in a misleading location, indicating only a southernmost inlet.
See also: Lossoth.