Tolkien’s One Ring was destroyed in the fires of Mount Doom. The volcano, also called Orodruin, stands in Mordor and was the place where Sauron originally forged the Ring.
Mount Doom’s fires are essential because the Ring cannot be destroyed by ordinary means. Its power is bound to the volcanic fire in which it was made, so the quest requires Frodo and Sam to cross Mordor and reach the Cracks of Doom inside the mountain.
At the decisive moment, Frodo claims the Ring rather than willingly casting it away. Gollum then bites off Frodo’s finger, falls into the fire while holding the Ring, and destroys it accidentally. Sauron’s power collapses with the Ring, and his fortress Barad-dûr falls. The mountain’s Elvish name, Orodruin, means “Mountain of Blazing Fire.”