The cathedral is dedicated to the Virgin Lady, erected on the remains of Janus God. Here reside the relics of St. Thomas, the Apostle of Doubt and Faith. The relics were moved from India and then from the isle of Chios (Greece) towards Ortona, here local pilgrims received them with great Catholic zeal. People of Ortona commemorate the saint twice a year: on 6th September and during the Feast of Absolution in May, related to the plenary indulgence.
The cathedral was badly damaged during the II World war and then massively rebuilt: the valuable portal was reconstructed with few intact remains available. Inside the church are canvas representing St. Thomas made by Basilio Cascella and majolicas made by Tommaso Cascella. Next to the church it is possible to visit the interesting Diocesan Museum with archeological remains, paintings and sculptures.
In December 1859 Pope Pius IX honored the church with the title of minor basilica.