Linked to the tradition of sacred erudition, d'Engenio's guide constitutes the fundamental reference text, not only for all subsequent guides but also for art literature. The author's intent is to examine the sacred buildings of the city by telling their history, the origin of their foundation, the relics preserved, remembering saints and blesseds who are part of that history, the organization of the officiating clergy, the illustrious men whose memory is linked to that place and then move on to the transcription of the tombstones that are observed or that once were there.