The main church of the Jesuit Block, started in 1645 and consecrated in 1671. The street facade is austere but the interior is remarkable: an inverted wooden ship's-hull vault built in cedar and cypress, the work of a Belgian Jesuit who had been a shipwright before joining the order.
The gilded altarpiece, also of carved cedar, is one of the most elaborate Baroque pieces in colonial Argentina. The smaller Domestic Chapel next door, used by the Jesuits themselves, is even older and rarely crowded.