Built in 1709, the elaborately restored cathedral on the east of the plaza has an overhanging roof supported by 121 huge tree-trunk columns and a similar bell tower. It is decorated with golden baroque designs depicting flowers, angels and the Holy Virgin. Outside mass times, access to the church is via a small museum, which displays interesting historical photos of the church before and after it was restored in the 1970s.

　　If the church museum is closed, ask at the Museo Misional across the square; the same person is responsible for both.