Mount Lung

Mount Lung was one of the mountains in the south of the planet Gallifrey. (TV: State of Decay, PROSE: Timewyrm: Revelation, Cat's Cradle: Time's Crucible, Lungbarrow, The Three Paths) Though the Doctor's cousins called it Lung, (PROSE: The Three Paths) teachers at the Academy called it Mount Cadon. (PROSE:  Timewyrm: Revelation, Lucifer Rising, The Three Paths) The Fifth Doctor noted it was also known as Mount Rycadia. (AUDIO: Devil in the Mist) The legends of the unhappened days, like those recounted by Lady Nine Teeth, called it Mount Plutarch. The Hermit said that the name one called it would change the way it was climbed. (PROSE: The Three Paths)

It was Gallifrey's highest peak, (PROSE:  Timewyrm: Revelation) reaching up into the atmosphere past the violet clouds and hovering flocks of air diamonds into the transduction barrier. (PROSE: Lucifer Rising) Fields of tall, still grass grew on the mountain before haytime. (PROSE: Cat's Cradle: Time's Crucible) Its slopes were carpeted with tiny blue flowers that waved back and forth, searching the air for unwary lizards. (PROSE: Lucifer Rising) Sometimes, it was covered with grey snow. (TV: The Time Monster, PROSE: The Three Paths) The snow on the mountain had natural hallucinogenic properties, capable of making climbers see all manner of visions, including their past and future. The hallucinations made climbing the peak more difficult the further along you proceeded, and because of this, the Doctor never succeeded in reaching its peak despite numerous attempts. (AUDIO: Devil in the Mist) Mount Lung smelled of weanskrike and tristort, and its native fauna included owls, beatitudes, (PROSE: The Three Paths) tafelshrews, (PROSE: Lungbarrow, The Three Paths) and cobblemice. (PROSE: Unnatural History, The Three Paths)

It was the location of the Doctor's childhood home, (TV: The Time Monster, PROSE: Cat's Cradle: Time's Crucible, Lungbarrow, Unnatural History, The Three Paths) which was named "Lungbarrow" after Mount Lung. It stood near the Cadonflood River until it was reported vanished. (PROSE: Lungbarrow) At the mountain's base stood the Prydonian Academy. (PROSE:  Timewyrm: Revelation, Lucifer Rising, The Three Paths) Students were not supposed to climb the mountain, however, the Fifth Doctor recalled climbing Mount Cadon with friends on numerous occasions in his youth, and reasoned that they should not have built the Academy at its foot if they didn't want students to try. On one of his attempts to climb Mount Cadon, the Doctor was joined by Vansell, who broke his leg during the ascent. (AUDIO: Devil in the Mist)

The Hermit lived on the mountain and told stories to young Gallifreyans, including the young First Doctor. (TV: The Time Monster, Planet of the Spiders, State of Decay, PROSE: Lucifer Rising, The Three Paths) He continually sat under a bare, twisted tree near the mountain's summit. (TV: The Time Monster, PROSE: Lucifer Rising, The Three Paths) The First Doctor returned to the mountain to speak with the Hermit before his first regeneration. (PROSE: The Three Paths)

While considered to be in the south of the planet, (PROSE: Lungbarrow, The Three Paths) the mountain was in view of the Time Lord Capitol, (PROSE: The Three Paths) distinct from South Gallifrey's mountainous and fiercely wintry landscape (PROSE: The Scarlet Empress) of hermits and "stray cats" (PROSE: The Return of the King)

Behind the scenes
Mount Plutarch first appeared under that name in Death Comes to Time as the home of the Kingmaker; The Three Paths later specified that it was the same mountain as the one called "Lung" and "Cadon" in other stories.