It is the day of La Tomatina (Tomato Festival), said to be the biggest tomato fighting event in the world. Held in Bunol, a small town about 50km away from Valencia, it is the only time in the year filled with massive amount of people from all around the world.
I heard about this festival from an acquaintance about 3 months ago, and since it was happening around the time I was in Spain, I decided to plan my trip to Valencia around the event date, and get a first hand experience.