The sorceress Nimueh frequently performed her most powerful forms of magic (like hydromancy) within the confines of a cave. She animated a piece of clay shaped to resemble an Afanc and delivered it into Camelot's water supply from this cavern, as well as monitoring the aftermath of her various machinations from a stone scrying fount in the cave (The Mark of Nimueh). The High Priestess also prepared in this cave a poisoned goblet with Mortaeus flowers (The Poisoned Chalice).
Nimueh's cave is a large, dark and gloomy cave with a bowl of water on a tall stand in the centre, in which Nimueh can peer into other places by casting a spell over it.
- The location of the cave is currently unknown. Nimueh's cave may be located on the Isle of the Blessed because she is later found inhabiting the Isle (Le Morte d'Arthur).
- Vast caves exist beneath the Forests of Balor, and Nimueh is clearly acquainted with these caverns, as she lured Arthur Pendragon into their depths (The Poisoned Chalice).