Doctor Who: 10 Things Everyone Always Gets Wrong About The TARDIS
7. A New TARDIS Can Be Built
Despite being referred to as machines and ships, TARDISes are so much more than that. They're actually organic entities that are grown, not built.
In the short story The Nameless City, it's said that TARDISes are grown from seeds that were stolen from the Archons, a race that existed at the dawn of time.
In a deleted scene from Journey's End, the Tenth Doctor hands the Metacrisis Doctor a chunk of TARDIS, and tells him to grow his own. This supposedly takes thousands of years to do, but the DoctorDonna provides a faster workaround. Though this scene was cut from the final episode, Russell T Davies has stated that he believes it still happened, cheekily noting that, one day, he'll go and put it back in.
That was in 2008, and now he's the showrunner again. He could very well make good on that promise!
The comic-book The Lost Dimension notes that, on Gallifrey, all TARDISes are grown in a special location called the Time Travel Capsule Growth Foundry, which the Eleventh Doctor refers to as the TARDIS Shipyards.
It's difficult to imagine a TARDIS growing from a seed like some sort of bizarre plant, but clearly, that's exactly what happens.