At a cost of 24 million Euros, this was the most expensive Spanish film ever made until Agora (2009) surpassed it. Director Agustín Díaz Yanes called that amount enough for 'a European super-production and an American rubbish-production'.
The role of Inquisitor Emilio Bocanegra is played by a woman, veteran actress Blanca Portillo. This caused controversy, not so much because it might look disrespectful towards the Church, but because many fans could not see the point in doing something like this. Díaz Yanes said that he had had the idea of using a female actress from the beginning, because he saw 'that Great Inquisitor role' as something too cartoonish and black-and-white and wanted to introduce a fresh, less recognizable element to it, and still make viewers suitably uneasy about so powerful and fearful a character. He cited the Oscar-winning supporting role of Linda Hunt in The Year of Living Dangerously (1982), where she played a man, as an example of what he wanted to achieve. Incidentally, Blanca Portillo wears her hair very short in her next film, Volver (2006), as a result of having had it cut for this role.
The film is based on a series of novels written by former Spanish war correspondent Arturo Pérez-Reverte. He had the idea for the books when he had a look at his daughter Carlota's History book from school and saw that only one page was devoted to the 'Siglo de Oro', the years in the 16th-17th centuries when Spain was the world's dominating superpower. Carlota, then 12, helped her father research the period, and the first novel, published in 1996, was published with 'Arturo y Carlota Pérez-Reverte' as the author. Five novels were published before the film was shot, and the film is based in the most important episodes in all of them... and beyond. The sixth novel was published in Spain in December 2006, and Pérez-Reverte has said he has drawn some inspiration from the film for the upcoming novels.
Several years before the film was almost made with Antonio Banderas set to direct and star with a script by Enrique Urbizu.