The church has 14 side chapels and a trompe-l'œil ceiling. Up in the choir loft are the hand-carved 17th-century seats of molave, a beautiful tropical hardwood. Adjacent to the church is a small museum run by the Augustinian order, featuring antique vestments, colonial furniture, and religious paintings and icons. It was named a National Historical Landmark by the Philippine government in 1976. Together with three other ancient churches in the country, it was designated as part of the World Heritage Site "Baroque Churches of the Philippines" in 1993.