In Monty Python and the Holy Grail, Sir Galahad meets the women at Castle Anthrax.
The castle appears during Galahad’s separate encounter after he sees a vision of the Holy Grail. Its inhabitants invite him to stay, presenting the situation as a parody of the seductive episodes found in medieval romances.
Galahad’s extreme chastity makes the scene especially comic. He is rescued by Lancelot before the encounter can develop, although Lancelot misunderstands the situation and believes Galahad needs saving from danger.
Castle Anthrax is one of several invented locations in the film, alongside Camelot, Swamp Castle and the Bridge of Death. The name sounds plausibly medieval but is deliberately exaggerated for the film’s comic tone.