At the top of a steep hill on the left bank of the Biferno River lies the village of Guglionesi, inhabited by different populations throughout its more than two thousand years of history. Founded by the Italic people of Frentani, it was occupied for many centuries by the Romans before passing into Norman hands in the Middle Ages. The Termoli bishops also appreciated the isolated and easily defendable position of Guglionesi, and moved the diocese here during the frequent attacks of the Turkish-Ottoman fleet towards the Termoli settlement.
The identity of Guglionesi is very much linked to the religious faith of its inhabitants, as told by the church of S. Antonio of Padua, that of S. Nicola and the collegiate church of S. Maria Maggiore. The latter holds a crypt, in a form somewhere between Romanesque and Gothic: these walls have guarded the remains of the patron saint of Guglionesi, S. Adamo Abate since 1102. A Molisian priest who lived around the 11th century, S. Adamo Abate is celebrated in the city every year from 1 to 3 June with magnificent festivities in the square.