In the novel The Ancestor Cell, the Doctor encounters a fleet of battle TARDISes whose exterior dimensions are equivalent to their interior ones, and they're the size of the moon.
Off-topic, I know, but it kinda bugged me when they started referring to other Gallifreyan spacetime craft as TARDISes, because Susan said in "An Unearthly Child" that she coined the name from the English initials of "Time And Relative Dimension In Space" (indeed, that very line was heard in "Journey to the Centre"). And presumably she didn't learn English until after she and the Doctor left Gallifrey and started visiting Earth. Plus, of course, originally it was treated as a "ship" whose given name was
Tardis -- they would occasionally say things like "We need to get back to
Tardis," and it was only later that it became standardized as "the TARDIS," with the word becoming a generic name for that type of vehicle rather than the name of a specific one.
Actually the show was inconsistent about it for a while -- we saw them referred to by Gallifreyans as "TT capsules" in a couple of stories, but there were other references to "TARDIS" as a generic name before then, like mentions of "the Master's TARDIS." And then there was "The War Games," where the War Chief supplied knockoff time machines called SIDRATs, TARDIS spelled backward.
