Castel del Monte is one of the 50 UNESCO World Heritage Sites in Italy. Commissioned by Frederick II of Swabia in the 13th century, the castle is a huge octagonal structure that sits on a small stretch of the Murge plateau in Apulia. Universally considered an example of medieval architecture, Castel del Monte unites elements of diverse styles and traditions from different epochs in history. The mathematical and astronomical rigour of the castle’s design, based on eight as a guiding number, and its position, studied so as to create symmetries of light during the winter solstice and summer equinox, have been attracting visitors and scholars for centuries.