This non-fiction monograph by Mario Signorelli presents a focused historical and architectural study of the Church of San Sisto in Viterbo. Emphasizing medieval ecclesiastical architecture, the work traces the church’s origins, structural modifications, and artistic features. It integrates archival research, stylistic analysis, and local religious history to position the building within the broader context of central Italian heritage. The book is valuable for scholars of religious architecture, Viterbo’s urban history, and those interested in the preservation of lesser-known Romanesque structures.