The Basque witch trials of the 17th century represent the most ambitious attempt at rooting out witchcraft ever undertaken by the Spanish Inquisition. The trial of the Basque witches at Logroño, near Navarre in northern Spain, which began in January 1609 against the background of similar persecutions conducted in Labourd by Pierre de Lancre, was almost certainly the biggest single event of its kind in history. By the end some 7,000 cases had been examined by the Inquisition.
Although Logroño is not a Basque city, it was the setting for an Inquisition tribunal responsible for the Kingdom of Navarre, Alava, Gipuzkoa, Biscay, La Rioja and the North of Burgos and Soria. Among the accused were not only women (although they predominated) but also children and men, including priests guilty of healing with nóminas, amulets with names of saints. The first phase ended in 1610, with a declaration of auto-da-fé against thirty-one of the accused, eleven or twelve of whom were burned to death (five of them symbolically, as they had died before auto-da-fé).
Thereafter proceedings were suspended until the inquisitors had a chance to gather further evidence on what they believed to be a widespread witch cult in the Basque region. Alonso Salazar Frias, the junior inquisitor and a lawyer by training, was delegated to examine the matter at length. Armed with an Edict of Grace, promising pardon to all those who voluntarily reported themselves and denounced their accomplices, he traveled across the countryside during the year 1611, mainly in the vicinity of Zugarramurdi, near what is now the French-Spanish border, where a cave and a water stream (Olabidea or Infernuko erreka, "Hell's stream") were said to be the meeting place of the witches.