On a hill of the Murge in Apulia, near the town of Andria, rises a building unlike any other medieval castle. Seen from above it is a perfect octagon, with an octagonal courtyard and eight octagonal towers at the corners. It has no moat, no drawbridge, none of the defensive structures typical of a fortress. It is Castel del Monte, commissioned by the emperor Frederick II of Swabia, and for centuries it has raised questions to which no one has given a definitive answer.
A building of the emperor
Frederick II was one of the most complex figures of the Middle Ages: king of Sicily, emperor, lawgiver, passionate about the natural sciences and author of a famous treatise on falconry, the De arte venandi cum avibus. At his court scholars of Latin, Greek, Arabic and Jewish culture met.
A document of 1240 records an order from the emperor concerning the building's construction. We do not know for certain when the work was completed, nor whether Frederick ever stayed there for long. In 1996 Castel del Monte was inscribed on the UNESCO World Heritage List, and its image appears on the Italian one-cent euro coin.
The geometry of eight
The whole building is built on the number eight:
| Element | Number |
|---|---|
| Sides of the outer perimeter | 8 |
| Sides of the inner courtyard | 8 |
| Corner towers | 8, each with an octagonal plan |
| Rooms on the ground floor | 8 |
| Rooms on the upper floor | 8 |
The rooms are trapezoidal and are arranged like segments around the courtyard. Moving from one room to the next creates a circular route, which partly follows a fixed direction: not all rooms communicate directly with the courtyard or with one another.
The repetition of the octagon at different scales, from the courtyard to the towers, gives the building a coherence reminiscent of a crystal: the same form reflected large and small.
Why the octagon
In medieval symbolic tradition the octagon holds a special position. It is the figure that lies halfway between the square and the circle: it is obtained by cutting the corners off a square, and with eight sides it already visibly approaches the circumference. If the square represents the earth and the circle heaven, the octagon becomes the figure of mediation between the two.
The number eight also had a strong Christian value. It was the number of the eighth day, the one following the seventh day of creation, associated with resurrection and new life. This is why many baptisteries and some imperial chapels had an octagonal plan. The Palatine Chapel in Aachen, built for Charlemagne, is built around an octagon, and the crown of the Holy Roman Empire is also octagonal.
For an emperor who saw himself as heir to Charlemagne and the Caesars, choosing the octagon could mean asserting a link between earthly power and a higher order.
Theories about its purpose
What Castel del Monte really was remains debated. The main hypotheses are:
- A hunting residence, linked to Frederick's passion for falconry and to its isolated position in the landscape.
- A building of representation, meant to display the emperor's prestige and culture.
- A symbolic construction, conceived as a geometric image of a cosmic or political order.
There is no shortage of bolder readings, which see the castle as an astronomical observatory or an initiatory place, and which study the shadows cast by the walls on the days of the solstices and equinoxes. Some observations are interesting, but no source of the time confirms any such use. It is more honest to regard them as possible keys to interpretation, not proven explanations.
Water and materials
An often overlooked detail concerns the care taken over water: the castle had cisterns and a system for collecting rain, important in an area poor in springs. The materials, too, tell of a precise choice. Local limestone was accompanied by elements in coral breccia, a reddish stone, and in marble, used for portals, columns and facings, creating contrasts of colour that are now partly lost.
These elements remind us that medieval sacred geometry was not abstract: it was realised with chosen stones, collected water and light entering through oriented windows.
What it tells us today
Castel del Monte is a rare example of a building in which geometry does not serve an obvious function but seems to be the message itself. Maestro Cornelio points to it as a place to be walked through slowly, room after room, letting the rhythm of eight guide one's attention from the perimeter towards the courtyard, that is towards the centre open to the sky.
In short
- Castel del Monte was commissioned by Frederick II; a document of 1240 records its construction.
- The plan is an octagon with an octagonal courtyard and eight octagonal towers, on two floors of eight rooms.
- The octagon is traditionally the figure of mediation between square and circle, earth and heaven.
- Eight recalls the eighth day of the resurrection and imperial chapels such as the one in Aachen.
- Its original purpose remains debated: hunting residence, building of representation or symbolic construction.
