Diamond Cave

The Diamond Cave is a cave in the Dornish Marches.

Background
During the reign of Aerys II Targaryen, a band of outlaws known as the Bandit Lords kidnapped Lord and Lady Dondarrion and held them in the Diamond Cave. Ser Arthur Dayne then slaughtered the outlaws and rescued the Dondarrions.

Season 8
Brienne, now Lord Commander of the Kingsguard, flicks through The Book of Brothers and briefly comes across Arthur Dayne's entry, in which the Diamond Cave is mentioned.

In the books
In the A Song of Ice and Fire, this cave is not mentioned.