Lake Vortigern

Lake Vortigern was a body of water located in England, outside Carbury. It was said that King Arthur of England obtained the legendary sword Excalibur from the Lady of the Lake whose hand had risen from the Lake holding onto the sword.

At the bottom of the lake was a transdimensional ship which contained King Arthur's suit of armour, a note from an alternative future Doctor, and an energy creature which functioned as the ship's defence system. The ship could be accessed by an underground tunnel. (DW: Battlefield)