Caerdroia

 was a crucial place in the Divergent Universe. Its name was a Welsh word that meant, according to the Eighth Doctor, "the fortress of many turnings... a maze." It had a castle, as the Kro'ka said, everywhere. This castle was, the Doctor surmised, the "home office" of the Divergence. Ultimately, was where the Doctor was reunited with his TARDIS after an extended time living in the Divergent Universe without it. (AUDIO: Caerdroia)