In preparation for the event, beginning March 1, there's a daily mascleta (gunpowder explosions) in the Plaza del Ayuntamiento (city hall) that booms and vibrates throughout the city. The streets are decorated with lights and there are spectacular light and music shows.
Fallas refers to both the celebration and the sculptures burned during the celebration. Beautiful, massive sculptures are built over the course of a year, viewed by the public for four days, judged in a competition, then set on fire and burned to the ground. It's difficult to understand why such magnificent art is burned, but it's part of the culture of Valencia. The burning is a symbolic rite of cleansing away the bad things of the old year and starting the new year fresh and clean.
Read more about the history of Las Fallas here: