Castel del Monte Structural Function
While the architects of tall cathedrals were preoccupied in building taller structures and necessarily making them leaner, the architect of Castel del Monte focused on a two-story building, following a clean geometric style that Götze calls the Hohenstaufen architecture (Götze 1998, 29-108).
This gives Castel del Monte the weighty quality typical of Romanesque architecture. The weighty character was in part a requirement for a two-floor construction; while the cathedrals are taller, they are one vault structures in height.
Castel del Monte represents a different architectural venture. While the builders of tall cathedrals looked at new solutions for lateral thrusts such as the flying buttresses, the architect of Castel del Monte looked instead at the geometry of the octagon to achieve the same pier and strut effects for lateral thrusts.
The enigmatic questions on the purpose and function of such an exquisite construction at Castel del Monte may indeed be tied to the geometric plant design and how it dealt with lateral thrusts. Given the historical context and the uniqueness of this construction, the architect of Castel del Monte was clearly indulging in exploring and exploiting the geometric properties of the octagon to solve the lateral thrust problem, opening up some new and unique approaches.
The construction issue posed by lateral thrusts may not seem significant enough for an entire edifice to be dedicated to its exploration. Historical monuments that we are left to study and admire are the most successful structurally, marginalizing the structural question and leading scholars to focus on the artistic features. Various scholars, exploring the purpose and function for Castel del Monte, have come to the conclusion that it may very well have been an architectural work for the purpose of architecture, a building without any other purpose (Willemsen 1984, 8 and 31; Cardini 2000, 28-29, 73, and 91).
The singular inspiration for this castle may have come from Frederick II himself: the emperor with a unique personal experience as a boy king that grew up in Sicily where he was exposed to Arabic culture rich in arithmetic and geometry; his admirastion of Muslim architectural works during his crusade that took him to Jerusalem; and his multicultural court that is said to have included the most notable mathematicians and philosophers of the time, from northern Europe to the Middle East.
Historians note that Frederick II maintained close ties with Leonardo Fibonacci, noted in the field of mathematics for the Fibonacci sequence and having introduced the Arabic numerals to the Western world, including the symbol for zero (Götze, 1998, 26).
The plant octagon that is only visible looking down from the sky may indeed be the explanation for this castle, as a unique and special construction where the Emperor intended to realize a new architectural solution in conjunction with his religious and political aspirations. In conflicts with the Papacy, Frederick II held singular opinions on the king's god-given secular powers separate from the religious power held by the pope (Cardini 1974, 83).
Castel del Monte is a unique structure in medieval architecture, unique even within the prolific castle building of Frederick II that counts more than 200 castles and palaces (Götze 1998, 29). Castel del Monte represents the zenith of Hohenstaufen architecture (Götze 1998, 209).
However, Castel del Monte is most exceptional because it integrates the special octagon solution to lateral thrusts into a geometric process for the plant design, a strict geometric procedure that turns into a mathematical design model. A new study looks at the plant design from a structural perspective, interpreting the layout as a solution to the lateral thrusts. The plant design is decoded from the existing layout and dimensions, a blue-print cast in stone.