The Cathedral of the Immaculate Conception sits on a hill in the centre of Boac, fortified against Moro raids in the 17th century and still largely intact. The thick stone walls, buttresses, and elevated position give it the look of a fortress as much as a church — a feature common to Spanish-era churches in coastal Philippine towns that faced regular pirate attacks. The current structure dates mainly from the 18th century, though a church has stood on the site since 1580.
Inside, the cathedral is cool and relatively bare, with a painted ceiling and a venerated image of the Virgin. The view from the church grounds over the Boac River and the surrounding town is the best elevated view available without climbing a hill. The cathedral is the focal point for Moriones Festival processions during Holy Week and the venue for masses that draw much of the island's population.