The 'fallas': 15 to 19 March

The Fallas ("Falles" as stated traditionally, in Valencian) is a festival held from 15 to 19 March in some cities and towns of Valencia (Spain), mainly including Valencia and Alcira, are held in honor St. Joseph, patron saint of carpenters. It is classified as a festival of international tourist interest. The fault name corresponding to the artistic buildings of combustible materials as a whole, representing figures known as 'ninots' and compositions of elements.
Throughout history, the materials have evolved, but traditionally, these ninots were paper, cardboard and wood. Currently the figures are more voluminous white cork, allowing lighter forms and larger.

Maybe it's a good idea to bear out the wikipedia in English or google-translated Spanish Wikipedia  If you are planning to visit Valencia on these dates.

In the North Station and the town square planned gifts usually have stewards with information on "Fallas" (indicate which are the "Fallas" and the prizes they have won each of them.)

Furthermore, in the town square, is made every day, the "mascletá" one of the largest fireworks displays in Europe and probably in the world, and one or two nights before burning these monuments of cardboard and cork, is made "la nit del foc", a nightly fireworks show over half an hour.