The Cathedral of Saints Nazario, Celso and Vittore, known as the Cathedral of Trivento, stands on an area of worship with ancient origins, built on the remains of a pagan Roman temple. Legend has it that it was St. Ambrose, in 398, who favored the translation from Milan to Trivento of the relics of the martyrs Nazarius and Celsus. The present building was built in the 11th century and was solemnly consecrated on May 15, 1076, as recalled by a plaque placed at the entrance.
Over the centuries the church has undergone numerous interventions and renovations, especially in the Baroque period and in the 18th century, which enriched its appearance. Today’s façade, in neoclassical style, dates back to 1905: an elegant portal with cornice and tympanum opens in the lower part, while a mosaic enclosed by a cornice stands out at the top; next to it, the bell tower soars.
The interior is divided into three naves separated by pillars with pointed arches, embellished with fine 18th-century stucco work. Also dating from the 18th century are the majestic high altar (1743), the wooden choir, and the paintings that adorn the chancel.
Of exceptional art-historical interest is the crypt, dated between the 11th and 12th centuries and dedicated to St. Castus. A Roman inscription in honor of Diana is preserved at the base of a pillar, confirming the presence of an earlier pagan temple. The space, divided by bare columns into seven small naves, holds 14th-century frescoes, a wooden statue of the enthroned Madonna and a stone bas-relief depicting the Trinity between angels and dolphins, also from the 13th century. More recent excavations have also unearthed the remains of an ancient baptistery, further evidence of the long and layered history of this sacred place.