Just watched Luis Buñuel’s 1950 film Los Olvidados (The Forgotten; film known in English as The Young and the Damned), about street children in Mexico City. Although it is very bleak social realism, very unlike his later surreal work, it has a mesmerising dream sequence half way through. Available in the US on Prime and elsewhere on YouTube: https://youtu.be/DX1uyJUa1o8.

Very much recommended! Further details with spoiler alert on Wikipedia, and pieces on it at many websites, especially about the role of chickens in the film!
https://en.m.wikipedia.org/wiki/Los_Olvidados