Religious drama was a specific type of theatre that developed in Europe during the Middle Ages, probably beginning in the 9th century. First performed in Latin, inside churches with very simple staging, between the 14th and the 15th centuries, religious drama started to be put on in different vernacular languages, both inside churches and outside, along streets and in public squares. Additionally, the staging became more complex, making use of floats, carriages and machinery for special effects. The latter was used especially for flying angels, sudden apparitions of demons from underground, or holy characters from the Heavens.
In Florence, the use of such machinery led to a special technical development beginning in the early Quattrocento (the 15th century), when complex artificial Heavens were built inside the churches of the south bank of the River Arno (Oltrarno) for the Ascension, Pentecost and Annunciation feasts. More specifically, the Ascension Feast was performed in the church of Santa Maria del Carmine, the Pentecost in Santo Spirito, and the Annunciation in San Felice in Piazza.