Buñol is a town of about 9,000 people in eastern Spain. On the last Wednesday of August, around 20,000 visitors join in and the streets turn bright red. Lorries drive in mountains of overripe tomatoes - ones that aren't good enough to sell - and tip them into the crowd. A bang signals the start. Another bang exactly one hour later signals the end.
There are rules. You have to squash each tomato in your hand before you throw it, so it doesn't hurt anyone. You can't bring anything else to throw. When the second bang goes off, everyone has to stop, even mid-throw. After that, fire engines and townspeople appear with hosepipes and brushes to wash the streets and the visitors clean.
Nobody is completely sure how the festival started. The most popular story says it began in 1945, when a group of friends got into a tomato fight at a town parade by accident. They had so much fun that they came back the next year on purpose, and the next, and the next. Eventually the whole town joined in.
The tomatoes used are special - a kind called 'tomate de Buñol' that is too soft to sell to shops, so the festival turns waste into a giant party. Buñol locals close their shop windows with plastic sheets, the streets get a good clean, and the tomato juice is actually good for the cobblestones.