Rectangular space with high ceilings (measured in plan and converted to Vitruvian measures, probably 2 x width 12p = 24p; the equivalent of 7.1m) arising from the construction of the mannerist sacristy, giving access to the staircase that served the upper floors. Here are kept vestments and liturgical implements, and the large canvas by António Gonçalves 1876 from the chancel. Relics were transferred from Flanders from the monastery of S.Marcos in 1595 to an emblematic space that existed in the cloister of Manga. These relics are said to have come to this chapel-reliquary in the 1630s. Of note is a silver reliquary with the skull of S. Teotónio, and another with the relics of the five Martyrs of Morocco