Pocket universe According to the Eleventh Doctor , a pocket universe or pocket dimension was a " distorted echo of our own " universe . He indicated such realities occurred spontaneously but that they " never last [ ed ] for long " . However , there were also examples of artificially created and longer lasting pocket universes . The Doctor also emphatically told Clara that a pocket universe was not a parallel universe . ( TV : " Hide " ) Nonetheless , the planet Gallifrey and the people on it were sent into was referred to by the War Doctor as being a " single moment in time , held in a parallel pocket universe . Like a painting ! " ( TV : " The Day of the Doctor " ) Because of their short lives , pocket universes were highly dangerous to the TARDIS , which could only survive for a few seconds before being inexorably trapped there as the universe collapsed back into the quantum foam . ( TV : " Hide " ) While the terms " pocket universe " and " pocket dimension " may have been interchangeable , Albert Marsden commented that he was not trapped in a whole universe , nor a whole planet , explaining that his " pocket dimension " / time loop merely stretched for five miles and ten days before restarting . ( AUDIO : " Protect and Survive " ) Examples . The Divergent Universe was a pocket universe that had no concept of time . Rassilon considered it the most " significant " of the universes he kept inside his dungeon on Gallifrey . ( AUDIO : " Zagreus " ) A dangerous species from the Dark Times was closed by other races in a pocket universe called the Ringpull . They were released by the Fifth Doctor and Turlough . ( AUDIO : " Ringpullworld " ) The Galacti - Bank vault utilised dimensional transcendentalism . The contents of the vault were contained in a pocket universe which could only be accessed by using the correct combination , which changed four times per day . ( AUDIO : " The Selachian Gambit " ) The Seventh Doctor trapped two Elder Gods in a pocket dimension that comprised of just five miles of Britain after a nuclear war . ( AUDIO : " Protect and Survive " ) Hila Tacorien was once trapped in a pocket universe , and was only brought back to the normal universe thanks to the work of Emma Grayling , an empathic psychic who was able to , as the Doctor put it , act " like a lantern , shining across the dimensions , guiding her home " . This pocket universe contained a large island seemingly floating in space , on which was a misty forest . Time also ran much slower in this pocket universe than in the prime universe , to the point that 1 second in the pocket universe was equivalent to 100 , 000 years in the Doctor ' s universe . ( TV : " Hide " ) The Celestial Toyroom ( TV : " The Celestial Toymaker " ) and the Land of Fiction were thought to be pocket universes . ( TV : " The Mind Robber " ) In order to save it from the Daleks , " all thirteen " incarnations of the Doctor teamed up together to freeze Gallifrey in time and place it in a " [ s ] ingle moment in time , held in a parallel pocket universe . " While they were unsure if they succeeded , an encounter with the Curator indicated to the Eleventh Doctor that this was in fact successful . According to the General and the Doctors , the calculations necessary would take several hundred years so the Doctor worked on them for all of his various lives . ( TV : " The Day of the Doctor " ) A doorway to this pocket universe in the form of a crack in time appeared in the town of Christmas on Trenzalore . It was through there that the Time Lords sent the message " Doctor Who " , which attracted the Eleventh Doctor as well as various races across the universe , and , 900 years later , with the Doctor dying from old age at the end of his final incarnation , energy for a new regeneration cycle . ( TV : " The Time of the Doctor " ) The Vess kept a weapons factory in a pocket dimension , powered by energy drawn from the Big Bang . ( AUDIO : " The Light at the End " ) Shadow - Space was an artificially created pocket dimension that stored the consciousness of intergalactic starship crew to protect them during warp flights . ( AUDIO : " Masquerade " )