Seventh Transept

The Seventh Transept was where the Headless Monks stored their leftovers: the heads of converts to their order. Most of them rotted to skulls. They were very active and ate (or at least killed) rats and intruders. The heads of richer converts, however, such as Dorium Maldovar, were stored in boxes, perfectly preserving them.

The Eleventh Doctor once went to the Seventh Transept to ask the head of Dorium Maldovar why the Silence wanted him dead. The Doctor later returned to the Transept with Dorium's head. (DW: The Wedding of River Song)