The Cathedral was built in 1080 on the place where there was the ancient Church of Sancta Maria de Neritorio, founded by monks from Middle East, who had fled because of iconoclastic persecution during VII century A.D. The Church is dedicated to Beata Vergine Santissima Assunta.

It has been a national monument since 1897 and a minor papal basilica since 1980. The Church has a basilica-ground-plan, subdivided into three naves. The columns and the walls are frescoed with valuable paintings from XIV and XV centuries. At the end of the central nave, there is the main altar, with pews in walnut wood. There is also a wooden Crucifix of XIII century, knows as the Black Christ for the dark colour of the cedar wood. It is said, without historical or documentary support, but certainly in a devotional spirit, that in 1255 the Saracens arrived in Nardò to conquer it, choosing as a symbolic act to burn the crucifix in the square.

While being transported outside the church, the crucifix hit the doorpost and a finger was completely severed by the impact. A lot of blood spilled from it, which terrified the Saracens, who gave up the plan. In 2013, to celebrate the 600th anniversary of the Cathedral, the Italian Post office issued a 70 cents stamp.