Located in Puglia, Castel del Monte (Italian for “Castle of the Mountain”) was built in the 13th century by Emperor Frederick II, who had inherited the lands from his mother Constance of Sicily. Frederick was responsible for the construction of many castles in Puglia, but Castel del Monte’s geometric design was unique. The emperor imbued it with symbolic significance, as reflected in the location, the mathematical and astronomical precision of the layout (studied so as to create symmetries of light during the winter solstice and summer equinox) and the perfectly regular shape (which uses eight as a guiding number). 

Built on a rocky hill overlooking the Murge plateau in southern Italy near the Adriatic Sea, the fortress is an octagonal prism with an octagonal tower at each corner. Both floors have eight rooms and an eight-sided courtyard occupies the castle’s center. The castle’s symbolism still intrigues scholars.

In the 18th century, the castle’s interior marbles and remaining furnishings were looted. The Castle’s interior features high, cross-vaulted ceilings, but has none of its original decorations. 

It has neither a moat nor a drawbridge and some scholars have argued that it had never been intended as a defensive fortress, but rather a hunting lodge; however, archaeological work has suggested that it originally had a curtain wall.

As explained on the UNESCO World Heritage website, “the site is of outstanding universal value in its formal perfection and its harmonious blending of cultural elements from northern Europe, the Muslim world, and classical antiquity. Castel del Monte is a unique masterpiece of medieval military architecture, reflecting the humanism of its founder, Frederick II of Hohenstaufen.”

(Fun fact: Castel del Monte appears on the Italian version of the one-cent euro coin).