Ceiling is gilded with gold brought from the New World.
The Holy Door into Santa Maria Maggiore. They are ceremoniously opened during Jubilee years designated by the Pope, for pilgrims who enter through those doors may piously gain the plenary indulgences attached with the Jubilee year celebrations.
Santa Maria Maggiore (aka. Basilica of Saint Mary Major) was built around 431AD. It is one of the four major basilicas. The church also contains the tomb of Bernini and several Popes.