Iron Mountains

The Iron Mountains, called Ered Engrin in the Elvish tongue, are a vast range running across the north of Middle-earth, and the cold about them is bitter. Melkor raises them when he returns to Arda, and behind their wall, out of reach of the light in the north, he delves his fortress of Utumno; Angband is cut into the same range some way west of it. After the Lamps are thrown down the chain runs on to meet the Blue Mountains in the west and the Orocarni in the east. Through the wars of the First Age the mountains cover Morgoth's back, so that he need look only southward. No Elf crosses them, for the heights are deadly and the winds foul, yet his spies find their way south by roads no one else knows.