The Iron Mountains.
From the most Northern of Arda to the plains of Ard-Galen and from Helcaraxe and Belegaer to the East-Sea beyond the Orocarni raises the plateau of Ered Engrin into Dor-Daidelos; the Region of Everlasting Cold. From Ered Engrin stretches out towards South; Ered Luin, Hithaeglir and the Orocarni. In the North-West of where the plateau of Ered Engrin falls down to the plain of Ard-Galen delved Morgoth Angband and raised the three tall towers of Thangorodrim. When the great war ended the First age and Thangorodrim and Angband were destroyed most of Ered Engrin were broken and laid waste but small parts of it stood still in the Second and Third age, thiese were the Mountains of Angmar and Ered Mithrin. The huge plateau of Dor Daidelos crumbled and sank and the remnants of it in is Forodwaith; the Northern Waste.