In J.R.R. Tolkien’s fantasy novel The Lord of the Rings, the One Ring was forged in Mount Doom.
Mount Doom is a volcanic peak in Mordor, the realm controlled by Sauron. Its fires are called the Cracks of Doom, and they possess the same destructive power required to unmake the Ring. This makes Mount Doom the only place where the Ring can be destroyed.
Sauron forged the One Ring there during the Second Age, linking much of his power to it. In the Third Age, Frodo Baggins and Samwise Gamgee travel to the volcano after crossing Mordor. Mount Doom is sometimes confused with Mount Caradhras, a dangerous mountain in the Misty Mountains, but Caradhras never served as the Ring’s forge.