From the United Nations Educational, Scientific and Cultural Organization (Unesco):
The mystery play of Elche is a sacred musical drama of the death, the passage into heaven (known as the Assumption) and the crowning of the Virgin Mary. Since the mid-fifteenth century it has been performed in the Basilica of Santa Maria and in the streets of the old city of Elche, situated in the region of Valencia. It is a living testimony of European religious theatre of the Middle Ages and of the cult of the Virgin.
This theatrical performance, which is entirely sung, comprises two acts, performed on 14 and 15 August. These depict the death and crowning of the Virgin in a series of scenes and related paintings: the death of Mary, the night procession that is followed by hundreds of participants carrying candles, the morning procession, the afternoon funeral procession in the streets of Elche, and the enactment of the burial, Assumption and coronation in the Basilica.
Mystery Plays and Passion Plays inside a church were not uncommon before the Protestant revolts, but were severely curtailed after the Catholic Reformation. The Mystery Play of Elx (Misteri d'Elx in Valencian/Catalan, Misterio de Elche in Spanish) was a rare exception after Trent allowed specifically for the Basilica of Saint Mary in Elx (Alicante, Valencia) by Pope Urban VIII. All participating actors are still today men, not women, as it has been since its inception, most probably in the 15th century.
Below, Jordi Savall's versions of one of the main compositions of the play, Esposa e Mare de Déu, and of the processional hymn, with images of the play and its traditional special effects, as well as the procession:
As the Valencians would say, Vixca la Mare de Déu!
[Video tip: Ex Orbe]