Why Caernarfon Castle looks different from every other Welsh castle

What is actually different about it

Stand at Conwy, Harlech or Beaumaris and you see a family resemblance: round towers, fairly uniform grey local stone, walls that read as one continuous surface. All three were built for the same king, in the same decades, under the same master of works. They look like siblings.

Caernarfon does not. Three things set it apart:

• Polygonal towers. Caernarfon's towers are many-sided rather than cylindrical — angular in plan, with flat faces meeting at corners. Round towers were the standard defensive form of the period because they deflect missiles and have no vulnerable corners to undermine. Choosing polygonal was a decision, not a default.
• Banded masonry. Horizontal courses of contrasting stone run through the curtain walls, producing visible stripes of lighter and darker material. Nothing about this improves the wall. It is surface treatment, and it is expensive surface treatment on a structure this size.
• Eagle sculptures. Carved stone eagles were set on the turrets of the great western tower — which is why it is the Eagle Tower. No other Edwardian castle in north Wales carries anything comparable.

Add the sheer scale of the King's Gate frontage facing the town, and the pattern is consistent: Caernarfon was built to be looked at as well as defended.

The Constantinople theory

The best-known explanation is that Caernarfon was consciously modelled on the walls of Constantinople — the fifth-century Theodosian Walls, which are built in alternating courses of stone and red brick and studded with polygonal towers. Photograph a stretch of the Theodosian Walls and a stretch of Caernarfon's south curtain and the visual rhyme is immediate.

The argument runs roughly like this. Constantinople was, in medieval European imagination, the surviving capital of the Roman Empire — the physical embodiment of imperial legitimacy. Edward I had been on crusade in 1270–72 and moved in circles thick with people who had seen the city or heard it described in detail; crusader accounts of its walls circulated widely, and his queen, Eleanor of Castile, came from a court with its own strong Mediterranean and crusading connections. Building a Welsh fortress that echoed those walls would be a way of dressing conquest as the restoration of Roman order.

The Roman and legendary layer

What makes the theory more than a coincidence of appearance is that Caernarfon already carried Roman associations before Edward arrived. The Roman auxiliary fort of Segontium sits on the hillside just outside the town, occupied for roughly three centuries and still visible as earthworks and footings. Its Roman past was known locally and to the English court.

Medieval Welsh tradition went further. Breuddwyd Macsen Wledig — "The Dream of Macsen Wledig", one of the tales collected in what is now called the Mabinogion — tells of a Roman emperor who dreams of a beautiful woman in a fortress at the mouth of a river opposite an island, travels to Wales, finds her, and marries her. Macsen Wledig is generally identified with the historical Magnus Maximus, a Roman commander in Britain who declared himself emperor in AD 383. The fortress of the tale is understood to be Caernarfon.

There is also a chronicle report that during Edward's works the body of "the father of the noble emperor Constantine" was found at Caernarfon and reburied on the king's orders in the church. Whatever was actually dug up, the episode shows that an imperial-Roman story was being told about the site at exactly the moment the castle was going up.

So the imagery had somewhere to land. A castle at Caernarfon that looked Roman-imperial would speak simultaneously to English claims of legitimate succession and to a Welsh legendary tradition that already placed an emperor on that spot.

What's evidence, and what's interpretation

It is worth separating the layers honestly, because this theory is repeated so often that it is frequently presented as settled fact. It is not.

Solid: Caernarfon's banded masonry, polygonal towers and eagles are real and genuinely anomalous among the Edwardian castles. The Theodosian Walls do share those visual characteristics. Segontium and the site's Roman past are documented. The Macsen Wledig tale and its Caernarfon setting are documented. The reburial episode appears in a contemporary chronicle. The castle's design is clearly doing symbolic work of some kind.

Interpretation: that the specific reference point was Constantinople, and that Edward or his masons intended it. No surviving document records anyone saying so. The reading was developed by modern scholars — most influentially Arnold Taylor in the mid-twentieth century — and later historians have pushed back, pointing out that banded stonework appears elsewhere in western Europe and that a general vocabulary of Roman imperial reference does not require a single model. Some argue the design owes as much to the earlier Welsh princely stronghold on the site and to available local stone as to any eastern precedent.

The fair summary: Caernarfon was plainly built to look imperial, and the Constantinople comparison is a compelling and widely accepted way of explaining how — but it remains an interpretation of the building rather than something the builders wrote down.

The eagles, and which one is real

Worth knowing before you go looking. Three eagle sculptures were set on the turrets of the Eagle Tower, and they are the detail that most directly signals Roman imperial imagery — the eagle being the standard of the Roman legions.

Only one of the three is generally accepted as genuinely medieval, and it is badly weathered — six centuries of Menai Strait weather have worn it down to a shape you have to know to recognise. The others are nineteenth-century replacements, added during the Victorian restoration works that also repaired much of the tower fabric. If you are photographing them from the ward below, you are mostly photographing Victorian masonry.

They are also easy to miss entirely, being small, high up and against the sky. Look for them from the western side of the lower ward, or from across the water near the harbour, where the turret line is clearer.