The small Belgian coastal town of Knokke-le-Zoute once was the scene for one of the most impressive gatherings of the international film avant-garde, when it hosted the last three editions of the illustrious EXPRMNTL film festival (1963, 1967, and 1974). This article focuses on the particularities of the town where EXPRMNTL took place, most notably its casino, exposing how and why Knokke was such fertile ground for the international film avant-garde to explode during EXPRMNTL 4, a festival that left its mark on all subsequent debates about experimental film. It showed, as no other event has, that there are different bourgeoisies and different undergrounds and they can clash in many ways. Just as we still live with the heritage of May 1968 in Paris, in the experimental film world so too we still live with the aftermath of EXPRMNTL 4 in 1967 in the small town of Knokke. When the fifth edition of the festival happened in 1974, EXPRMNTL could not live up to its revolutionary reputation, and Knokke, with its casino, would never again be the experimental film capital of the world.