La Tomatina in Buñol
Bunol's late-August tomato fight, now capped and ticketed, in which thousands of participants throw roughly a hundred tons of overripe tomatoes through the town's central street for one strictly timed hour. Started informally in 1945 and now one of Spain's most internationally recognized festival exports.
La Tomatina matters because it proves communal nonsense can become heritage when a town repeats it with care, limits and laughter.