Doors of Angband

The ancient fortress of Angband stood to the North of the Iron Mountains, defended by them from the West and from Beleriand. When Morgoth returned to Middle-earth after the Darkening of Valinor, he raised up the three peaks of Thangorodrim to strengthen these defences even further, and made a long tunnel running southwards through the Mountains. At the southern end of this tunnel he made a great gate, an archway in the sheer cliff-face that opened into a dark valley, that in turn led out into the dark land of Dor Daedeloth. The Doors were guarded by the immense Wolf Carcharoth, set there by Morgoth to defend his realm against the Hound of Valinor.

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This great southern gate is the only real candidate to be the portal known as the Doors of Angband, but it should be noted that there are some mild inconsistencies between various sources. The description above comes from a detailed and explicit account in Quenta Silmarillion 14 that leaves little room for interpretation. Other descriptions, however, have the Doors opening directly onto stairs that lead down into Angband itself. For example, in Of the Fifth Battle: Nirnaeth Arnoediad (ibid 20), we're told that the Elves of Nargothrond '...burst through the Gate and slew the guards upon the very stairs of Angband...' without any mention of an intervening tunnel, and the account of Beren and Lúthien (ibid 19) describes a similar arrangement of 'labyrinthine stairs' immediately behind the Gate.

These accounts can be reconciled if we imagine that the stairs behind the Doors led down into the tunnel beneath the Iron Mountains, and then onwards and downwards into Angband itself at the tunnel's farther end, under the Northern Wastes.

It must be granted that this is not perhaps the most natural reading of the text, and more likely these variants represent different conceptions of Angband within Tolkien's writing. Evidence for this is found on a map from the 1930s (in volume V of The History of Middle-earth) on which the Iron Mountains are not shown as a range, but instead the peaks of Thangorodrim emerge directly from a simple circle of hills, so that Angband can be approached directly. At this point the story of Beren and Lúthien was already well established, so it seems that the idea of the long arc of the Mountains (and the tunnel this would make necessary) arose as part of a later phase of The Silmarillion.