In Medieval times
the town of Termoli was part of a dense network of international traffic because of its position on the coast along the itineraries that led to the popular
sanctuary of San Michele sul Gargano and the Holy Land. The cathedral is undoubtedly an important testimony of the town’s relations with Apulia, the Holy Land
and transalpine countries, particularly France, as is clearly demonstrated by the complex ornamentation of the façade.
The present-day building was built between the 12th and 13th centuries on the site of an older cathedral
(probably dating back to the 11th century), of which there are still remains of the western triapsidal body and of the rich mosaic floors of the naves and
presbytery. The present-day church is also triapsidal, and has a basilical floor plan divided into three naves by cruciform pillars. The presbytery is raised
high above the floor of the naves. The interior has suffered various transformations that have greatly altered its original appearance, while the modifications
made to the outside, which still preserves most of its original decorations, have been less significant. The decorations on the lower part of the façade are
particularly rich, presenting a series of blind arches, including two-light mullioned windows and a central portal. Both the arches and mullioned windows
feature architectural elements (arched lintels and capitals) ornamented with vegetal and figured patterns. Inside the first mullioned window from the left,
inserted in the back wall, two sculptures in high relief represent the Annunciation, while remains of another sculptured scene depicting the Presentation in the
Temple can be seen in the lunette on the portal. On the sides of the lunette, two shelves bearing inscriptions on the edges originally supported sculptures of
which only the statue of St. Basso still remains. Both inscriptions, as well as that found inside the lunette on the last mullioned window, refer to the person
who ordered the execution of the sculptures. A severely mutilated fourth inscription, located at the bottom of the lunette on the central portal, according to
some sources probably bore the name of the architect of the cathedral, Alfano from Termoli.