For 17th-century Catholics, the church nave was the spiritual heart of Mission San Gregorio de Abó. When worshippers, both indigenous people and nearby settlers from Spain, came to hear Mass, they stood and knelt because there were no pews, and prayers and sacred songs echoed off the walls. At the altar ahead, the priest chanted the familiar liturgy of the Mass in Latin, the same as in any Roman Catholic church in Europe, Asia, Africa, or the Americas in those years. The outline of stones on the ground ahead indicates the smaller size of this church in the 1620s, and construction twenty years later left Abó's sanctuary more as it appears now, with new walls reaching 50 feet high.