“Land Without Bread” (1933) IMDb
Some of the 52 hurdes, isolated mountain villages in pre-Franco Spain, where the human population suffers greatly from ecological marginalization, superstition and other horrors.
Las Hurdes is possibly the first mockumentary: partly accurate, politically serious, but partly staged like Nanook of the North (1922) and seemingly designed to ridicule the audience in a straight-faced parody of distancing colonialist anthropological documentaries. Lots of black humour, by surrealist Luis Bunuel. Read all you can about it; deeply fascinating stuff.
References here: Viridiana (1961).