The altar was brought from Mexico to this Mission. Note the Kneeler on the right side:
It was used 1987 by the Polish Pope John Paul II during his visit to the Mission.

If you are a Hitchcock fan: This is where some scenes of the classic "Vertigo" were filmed.
Kim Novak went through the door on the right to the sacristy toward the cemetery, and James
Stewart followed her there and later identified the (fictive) grave where she stood.