Caer Sidi

Also Known As: Middle Welsh Kaer Sidi; also Caer Siddi; usually read as “fortress of the síd”, the fairy mound, from Old Irish síd
Region/Culture: Northern Europe
Mythos: Welsh Mythology, Celtic Mythology
Primary Type/Nature: Mythological Places
Mythical Attributes: Caer Sidi is an Otherworld fortress ringed by the sea, where nobody falls sick or grows old and a spring runs with a drink sweeter than white wine.
Role in Mythos: It is the stronghold Arthur raids by ship in the poem Preiddeu Annwfn, the prison of the youth Gweir, and the seat of the poet Taliesin’s chair.
Relation to Humans: Mortals reach it only by sea and at terrible cost, since three shiploads of Arthur’s men sailed in and seven men came back. Those who belong inside it are spared disease and age, and one of them is held there on a heavy chain.

Three times the ship filled with men, and the ship was Prydwen, Arthur’s own. They sailed for a fortress across the water, and somewhere inside it a young man was singing in a chain. When the ship came home, seven were left to step off it.

That is nearly everything the poem says about the raid, and it says it more than once. Preiddeu Annwfn, The Spoils of Annwfn, is a short and difficult Welsh poem preserved in a single manuscript, the Book of Taliesin, copied in the first half of the fourteenth century and now kept at the National Library of Wales. The verses themselves are older, composed at some point between the ninth century and the twelfth. The voice is that of Taliesin, the legendary poet, who claims he was on board. He does not tell the story. He alludes to it, as if to an audience who already knew how it went, and then closes each stanza with the same grim count of survivors. In the first stanza the place they failed to come back from is Caer Sidi.

The name is half Welsh and half borrowed. Caer is a fort or stronghold. Sidi is most often explained as a Welsh form of the Irish word síd, the hollow hill where the people of the Otherworld live. So this is the fortress of the fairy mound, set down in the middle of the sea. An older generation of scholars, John Rhys among them, heard a Welsh word for turning in it and made it a revolving castle. That reading has faded, though the spinning tower it produced still turns up in popular retellings.

Inside the walls, the poem puts a prisoner. His name is Gweir, and the poet says his prison was made ready for him according to the tale of Pwyll and Pryderi, a tale that has not survived in that form. Nobody had gone into the place before him. A heavy grey-blue chain holds him, and he sings in sorrow in front of the spoils of Annwfn, a song that will go on until Doomsday. The poem never explains what he did or who put him there. The Welsh Triads remember a Gweir son of Geirioedd as one of the Three Exalted Prisoners of the Island of Britain, alongside Llŷr and Mabon, and the island of Lundy in the Bristol Channel was once called Ynys Weir, Gweir’s Island. That is as close as anyone has come to pinning the fortress to a map.

The next stanza turns to what the raiders came for. It is the cauldron of the Chief of Annwfn, dark around the rim and edged with pearls, warmed by the breath of nine maidens. It will not boil the food of a coward. From here on the poem keeps changing the fortress’s name while the body count stays the same: the four-cornered fort, the fort of mead-drunkenness, the glass fort, and others harder to translate. Whether these are eight strongholds or eight ways of naming one has never been settled. Most readers take Caer Sidi as a title for Annwfn itself, the Welsh Otherworld, seen from the deck of a ship that should not have gone there.

The same manuscript holds a second and much gentler glimpse. In a poem known as Kerd Veib am Llyr, the Song before the Sons of Llŷr, Taliesin boasts that his chair stands ready in Caer Sidi. Here the fortress is no prison. Sickness and old age do not touch anyone who is in it, and Manawydan and Pryderi know the place well. Around a fire in front of the chair there is music, three instruments by one reading and three songs by another. The cold streams of the ocean run around its corners. Above it rises a fruitful spring, and what flows from that spring is sweeter than white wine. It is an ordinary evening in a house where nobody ages: firelight, a seat kept for the poet, the sound of strings, salt water moving past outside.

Set the two passages side by side and the picture is odd. One fortress holds a warm hearth and a chained boy, a guest who will never grow old and a captive who will never stop singing. The poems do not try to reconcile this. Nor do they describe the building. There is no height given, no gate, no colour of stone, only corners, sea, fire and a spring. The glass fort and the four-cornered fort of the later stanzas may be the same walls under other names, or they may not.

How Caer Sidi came to exist is not recorded either. No builder is named and no founding story survives. It is simply there, as the Irish mounds are simply there, with the difference that this one has to be reached by boat. The echoes elsewhere in Welsh tradition are of the voyage and not the place: in Culhwch and Olwen, Arthur sails Prydwen to Ireland to seize a cauldron that will not cook for cowards, and in the tale of Branwen an army crosses the same sea over a cauldron and seven men return, Taliesin and Pryderi among them.

What the fortress can do follows from what it is. It keeps its own people beyond the reach of illness and time, it feeds them from a spring that never fails, and it holds a treasure that can tell a brave man from a coward. It also keeps what it takes. The chain on Gweir is heavy and nobody in the poem strikes it off.

Its limits are few, and Arthur found most of them. The sea around it can be crossed. Its cauldron can, it seems, be carried away, since the poem is named for the spoils. But the price was almost the whole of three crews, and the poet who lived to tell it spends the rest of his verses sneering at monks and scholars who do not know what he knows. Seven came back.

Frequently Asked Questions

What is Caer Sidi?

Caer Sidi is an Otherworld fortress in medieval Welsh poetry. It appears in two poems in the Book of Taliesin, where it is the stronghold raided by Arthur, the prison of Gweir, and the place where Taliesin’s chair stands. Most readers take it as another name for Annwfn, the Welsh Otherworld.

What does the name Caer Sidi mean?

Caer is the Welsh word for a fort or stronghold. Sidi is most often explained as a Welsh form of the Irish word síd, the fairy mound of the Otherworld, so Caer Sidi means the fortress of the fairy mound. An older reading that made it a revolving castle, proposed by scholars such as John Rhys, has faded.

Who was imprisoned in Caer Sidi?

A youth named Gweir was imprisoned in Caer Sidi. The poem Preiddeu Annwfn says he was held by a heavy grey-blue chain and sang in sorrow before the spoils of Annwfn, and that his song will last until Doomsday. The poem does not say why he was imprisoned.

What happened when Arthur went to Caer Sidi?

Arthur sailed to Caer Sidi with three shiploads of men in his ship Prydwen. The raiders went after the pearl-rimmed cauldron of the Chief of Annwfn, which will not boil the food of a coward. Only seven men returned.

Where is Caer Sidi located?

Caer Sidi has no fixed location. The poems place it in the sea, with the streams of the ocean around its corners. The island of Lundy in the Bristol Channel was once called Ynys Weir, Gweir’s Island, which is the nearest link between the fortress and a real place.