The relics of the martyr San Gaudenzio are preserved under the high altar of the parochial church of Valpromaro. A seal from 1648 confirms their authenticity and delivery to the Company of the Blessed Virgin of Miracles in Valpromaro. The saint is described as a young shepherd who was made a martyr for his faith in Christ under the rule of King Eurico, between the years 466 and 484. In the parochial archive they preserve the surveys carried out on the relics every one hundred years, the last one in 1925. The festival is celebrated every year on the last Sunday of August. As a testimony to the widespread worship of the martyr, the name Guadenzio was one of the most common in the town between the 17th and 19th centuries.

Sources: AAVV, Valpromaro a century of devotion, under the care of the country committee, Massarosa Offset typography, Massarosa, 2002.