From a series on Europe's Weird Ways in Der Spiegel:
Every year at the end of Carnival, the Greek village of Galaxidi erupts in a day-long flour war. Goggles and overalls are recommended.
Clean Monday is a hell of a misnomer in the Greek port town of Galaxidi. Indeed, by the time the day comes to an end, the coastal town, located some 200 kilometers west of Athens -- and just down the hill from where the Oracle of Delphi used to predict the future -- is covered in sticky, brightly colored flour. Villagers there mark the end of carnival season and the beginning of Greek Orthodox Lent by throwing over 3,000 pounds of flour at one another.