Orodruin
The One Ring was forged by the Dark Lord Sauron during the Second Age to gain dominion over the free peoples of Middle-earth. In disguise as "Annatar", or "Lord of Gifts", he aided the Elven smiths of Eregion and their leader Celebrimbor in the making of the Rings of Power. He then forged the One Ring in the fires of Mount Doom.