The interior of the Cathedral is impressively beautiful and has a vaulted ceiling. The body of the church is divided by two rows of pillars into a nave and two aisles.
The pillared nave is barrel-vaulted while the crossing is rib-vaulted which supports the choir.
From the vault hangs the national shield surmounted with imperial crown and one chandelier of 40 candles in the middle.
At the entrance are two marble basins inserted in the columns with the statues of St. Francis Xavier and St. Ignatius of Loyola. To the right there is a baptismal font which is of black stone. It is said that in this font the apostle of the Indies, St. Francis Xavier may have baptized a great number of people. On the left of the entrance there is a stairway leading to the choir.
Another remarkable object in this place is a large picture representing St. Christopher with the Infant Jesus on his shoulders. On 25" July of each year, the day dedicated to the commemoration of this holy martyr, the chapter offers thanks to the Saint for having saved through his intercession the rest of the Cathedral from destruction when one of its towers fell down.
Turning to the right we see four chapels the first dedicated to St. Anthony, the second to St. Bernard, the third to the Cruz Milagres and the fourth to the Holy Ghost. To the left of the entrance are four chapels, the first is dedicated to Our Lady of Virtues, the second to St. Sebastian, the third to Blessed Sacrament and the fourth to our Lady of Life. The chapels of the Blessed Sacrament and the Cross of Miracles are cloistered behind finely filigreed wooden screens.
As we proceed to the interior we find the transcept. It has six altars , three on each side. Those to the right are dedicated respectively to St. Anna, Our Lady of Doloures and St. Peter, while those on the left are those of Our Lady of Sorrows, Our Lady of Hope and Our Lady of Three Necessities.