Premise: Mount Doom is a fictional volcano in J.R.R. Tolkien's Middle-earth legendarium. It is located in the northwest of the Black Land of Mordor and close to Barad-dûr. Alternative names, in Tolkien's invented language of Sindarin, include Orodruin ("fiery mountain") and Amon Amarth ("mountain of fate").
Hypothesis: Mount Doom is an actual volcano located in the northwest of the Black Land of Mordor and close to Barad-dûr.