Castel del Monte is a 13th-century fortress built by the emperor of the Kingdom of Sicily Federico II in the plateau of the Western Murge in Puglia, in the present homonymous village of Andria. The origin of the building dates back to January 29, 1240, when Frederick II Hohenstaufen ordered Riccardo da Montefuscolo, Captain of Justice, to prepare the materials and everything needed for the construction of a castle at the church of Sancta Maria de Monte . Incerta is also the attribution to a precise architect: some recapture the work to Riccardo da Lentini but many argue that designing the building was the same as Frederick II. It seems that it was built on the ruins of a former fortress first Lombard and then Norman. Probably the death of Frederick II, the building had not yet ended. From the times of Emperor Federico to Giovanna I, queen of Naples, this splendid fortress was always called "Castle of Santa Maria del Monte". The first time that it was described without the title "Santa Maria", then simply "Castel del Monte" is in a decree of King Ferdinand of Aragon, dated from the Castle of Altamura on 1 December 1463. It was rarely used for parties; Among these in 1246 are the wedding of Violante, the natural daughter of Federico and Bianca Lancia with the Count of Caserta Riccardo Sanseverino. Castel del Monte was also a prison place. Under the jurisdiction of Charles I was imprisoned, secretly and under the custody of Castello Golardo Saumeri, Corrado Conte of Caserta and the small children of Manfredi: Enrico, Federico, Enzio. From the seventeenth century it followed a long period of abandonment, during which the castle was stripped of marble furniture and decorations, and also became a prison for shepherds, brigands and political refugees. In 1928, the restoration directed by the architect Quagliati removed the material from outside the castle and demolished some of the perishable structures, then reconstructed them to give the castle a "rejuvenated" appearance; this did not stop the deterioration and had to be further restored between 1975 and 1981. In 1936 Castel del Monte was declared a national monument. In 1996, UNESCO incorporated it into the World Heritage List for the mathematical and astronomical rigor of its forms and for the harmonious union of the cultural elements of northern Europe, the Islamic world and classical antiquity, a typical example of architecture of the Middle Ages. The building is octagonal. The interior space is divided into two floors, raised above the square in front of 3 and 9 meters respectively. The rooms, trapezoidal, are divided by walls joining the edges of the octogenous interior and the edges of the outer one, where the corresponding towers are set. The problem of covering the rooms is resolved by disassembling the initial trapeze into a central square and two lateral triangles. The central square is covered by a cruise ship, while the two lateral triangles are overrun by two clusters of barrel vaults for each room. At the center of each cruise, in the intersection between the ribs, comes out of the intradosso a "extradossata" turn key for each room. The ribs do not have a static, but decorative function. The barrel vaults are constructed following the pattern of the external walls relative to that part of the building. As far as adjacent, the two types of times used are completely independent: in the intersection between them, in fact, it can be noticed that the warping has a discontinuity caused by a phase-out in the composition of the two contiguous shells. The tax plan of the vault is underlined by a frame, also restored in the capital over the bearing columns.