The Batcave was Batman's fictional secret base of operations.
Professor Bernice Summerfield, undercover in the 46th century and debating her own existence with students Grayson and Gould, remarked that archaeology had never found other fictional people and places, including the Batcave. (PROSE: Paydirt)
Ace compared the TARDIS wardrobe to the Batcave, in terms of its immensity. (PROSE: Echo) Sarah Jane likewise thought the Eighth Doctor's console room to be "a great big Batcave of a place". (PROSE: Interference - Book Two)