The following are kept in this church: the remains of Saint Fulgentius and Saint Florentina, two saints so highly venerated that they even have their own Jubilee Year. The brother of Saint Isidore of Seville and Theodora, wife of King Leovigildo, its history dates back to the 6th century with the conversion of the Arian Visigothic monarchy to Catholicism.

Legend has it that his remains, carried by a group of clergymen who were fleeing Seville in the year 713 following the Islamic invasion, were buried in these mountains next to a “grey heather” bush – hence the name of the village – where they were discovered in the 13th century by a farm labourer whose plough struck an alabaster chest containing them.

A subsequent lawsuit brought by the city of Cartagena, which was claiming the relics on the grounds that the saints were natives of the city, was settled in a Solomonic manner by Philip II, who sent two large bones to El Escorial, two to Murcia and left the rest in Berzocana, for which He ordered a chapel to be built and donated the beautiful reliquary in which they are kept.