The Cathedral of Christ the King dominates Mullingar's skyline with its twin-towered Renaissance facade, completed in 1936 to a design by Ralph Byrne. It is one of the most significant Catholic churches built in Ireland in the twentieth century — monumental in scale, formal in composition, and deliberately imposing at a time when the new Irish state was keen to assert its identity. The interior is spacious and light, with high vaulted ceilings and side chapels that reward unhurried exploration.
The cathedral also houses a small ecclesiastical museum with vestments, silverware, and artefacts from the diocese, including a mitre associated with St Oliver Plunkett. Entry is free, and guided tours run in summer. Mass times are posted at the main entrance. Even if you have no interest in religion, the building's architecture and the quality of some of its internal fittings — particularly the floor mosaics — are worth the detour.