Popocatépetl
From Tardis Wiki, the free Doctor Who reference
Popocatépetl was a volcano the Fourth Doctor mentioned to Maren on Karn as an example of what might happen to the Sisterhood's convent if there was some geologic reason for the diminishment of the Sacred Flame. (TV: The Brain of Morbius)
Behind the scenes
Though unremarked in the serial, the volcano is in Mexico, close to Mexico City.
