According to Wikipedia, at the time of writing there are a total of 205 sovereign states; including those that are disputed. That’s at least 205 different cultures, so the question is: Are there any concentrations of peoples in the world that represent all of these? If I were to look, the first places which I’d examine are the so called “Global Cities”. The most prominent and, anecdotally, most diverse of which being London and New York City.
Now, suppose we can select 205 people from one of these cities, each representing their own home country, what now? Well, we’re all human and we all have stories, flavoured by our cultural heritage; so we write! That is, we set up a round-robin story where everyone in our group gets an equal share (e.g., a page each).
Potentially, all our authors would write in their own language, so we’d need a cohort of translators so everyone understands what’s going on, as well as producing a coherent end product. Furthermore, some kind of editorial control would need to be exercised, that steers and plans the characters and plot; however, beyond that, creative freedom is afforded to our authors.
An alternative — although much more ambitious — idea would be to focus on linguistic diversity, rather than sovereign cultures. This pushes the number of potential contributors through the roof and, with it, the potentially impossible task of translation! (Let alone the logistical burden of finding volunteers across the world.) Therefore, instead of writing a round-robin story, how about a dialogue-free film, where each person acts as screenwriter and co-director for a scene?