St Paul's Cathedral was a cathedral in the city of London, known for its large size and distinctive dome.
Encounters at the Cathedral
In 1561, the Silence built a time capsule disguised as a tower of the Cathedral, which the Eleventh Doctor and River Song stole and used to batter through a time lock in London in 2106. (GAME: The Eternity Clock)
During a visit to London in February 1814 with the First Doctor, Vicki Pallister noticed the dome of St Paul's Cathedral and mentioned that the cathedral still stood in the 25th century, having survived World War I, World War II, World War III, World War IV and the 22nd century Dalek invasion. (AUDIO: Frostfire)
Once, while the Twelfth Doctor and the Half-Face Man were grappling with each other at the door of the SS Marie Antoinette's escape pod in the 1890s, the escape capsule flew over St. Paul's Cathedral. (TV: Deep Breath)
After the death of Danny Pink, the TARDIS took the Twelfth Doctor and Clara Oswald to the base of 3W. The telepathic controls deducted that this would be the place where Clara and Danny would next meet. It was revealed that the base was filled with tombs containing dozens of Cybermen. Upon exiting, the Doctor realised that it was actually St Paul's Cathedral. (TV: Dark Water) The Twelfth Doctor noted to Kate Stewart that the cathedral was bigger on the inside thanks to dimensional engineering. They, along with UNIT soldiers, watched as the roof was lifted and let various Cybermen escape from their tombs inside it. (TV: Death in Heaven)
In an alternate 2586, Emily Blandish and Honoré Lechasseur's investigation of a mysterious murder led them to St Paul's Cathedral, which was deserted and rumoured to be haunted. The Cathedral was destroyed in an explosion caused by the death of the Daemon Mastho. (PROSE: Child of Time)
In an alternate timeline in which the Church of the Glorious Dead conquered all of Earth over its history, Sato Katsura allowed the ruined St Paul's Cathedral to remain as a warning to humanity against defying the Church's beliefs. Sato and Kroton briefly fought in and on the steps outside of the Cathedral during their battle. (COMIC: The Glorious Dead)
As basis of comparison
In an alternative reality in which Adric survived his crash-landing and death on prehistoric Earth, he used Block Transfer Computation to build himself a city, the entrance to which Beatrice Mapp compared in size to St Paul's Cathedral. (AUDIO: The Boy That Time Forgot)
In the 1980s, the Fourth Doctor estimated that the Krynoid enveloping Chase Mansion would soon grow to the size of St Paul's Cathedral, and after that eventually grow to envelop the entire Earth. (TV: The Seeds of Doom)
Behind the scenes
In the ultimately unproduced film The Dark Dimension, the Cybermen were to have been among several alien races seen to invade London and, in scenes echoing The Invasion, were to appear on the horizon of the steps of St Paul's Cathedral, all opening fire on humans as they ran for their lives.