In the south of Italy stands one of the most beautiful and fascinating castles of the Middle Ages, built by the brilliant Emperor Frederick II of the Staufen dynasty. Castel del Monte is truly extraordinary in the history of European architecture, and even today there are many different theories about the purpose of this exceptional castle. Most of these, however, are based more on speculation than on solid analysis, and none of these hypotheses have been accurate enough to penetrate and unravel the secrets of this distinctive geometric fortification. Castel del Monte is a study of the structure's enigmatic plan, singular in the history of art and architecture in terms of its construction. This beautifully illustrated book presents the reader with insights into the bastion's mathematical-geometrical structure and into architecture in general under Frederick II. The volume explores the cultural influences common to the entire Mediterranean region and the influence of the revered Arabian geometry of that time, and offers these factors as a context for the conception and construction of Castel del Monte. Castel del Monte is a scholarly, interdisciplinary study and assessment of this intriguing masterpiece of mediaeval architecture.