One of the Middle Ages’ most mysterious monuments can be found in the bucolic heart of Puglia in southeast Italy. Built on top of a 540-metre hill in the municipality of Andria, Castel del Monte is the legacy of Frederick II, Holy Emperor of Rome, and was completed in 1240. The mystery lies in the castle’s octagonal design, which many experts speculate was linked to the emperor’s fascination with astrology, physics and mathematics.

Frederick II was born in 1194, son of Henry of Hoenstaufen and Constance of Altavilla, the last descendant of the Norman dynasty. He grew up in Palermo – capital of the Norman Kingdom – and married Constance of Aragon, who brought him a dowry of 300 knights.