Incubus (1966)

According to Wiki, to date it's one of only four feature-length films to be made in Esperanto, a constructed auxiliary language created in 1887. So while that alone gives it an appeal, it's also interesting visually and conceptually, the strangeness being reminiscent of Bergman at times.
The B+W cinematography and otherworldly feeling of the island setting are complementary to the struggle between good and evil that's played out upon it, so even when it's being dull it at least looks beautiful. But quite often it's all too apparent that the actors are reciting lines learned phonetically; that constant intrusion of reality upon the fiction really compromised the all-important connection I was hoping to find with each of the characters.

3 black fibres out of 5