OTHER MYSTERIES · UK HISTORICAL CASE
Location: Dinas Emrys, near Beddgelert, Gwynedd, Wales
Period: Medieval written traditions; earlier setting in the age of Vortigern
A ruler’s building work disappears during the night. His advisers demand a child’s blood, but the child turns their explanation upside down: beneath the ground lies a pool, and inside it two opposing creatures. Dinas Emrys gathers this encounter, the legend of Lludd’s buried dragons and a real hilltop stronghold into one of Wales’s richest places of mystery.
Vortigern searches for a secure place
The Historia Brittonum, traditionally associated with Nennius, describes Vortigern searching the mountains of North Wales for a defensible site. His advisers choose a place where a citadel can protect him. Builders and materials are assembled, but by morning the work has vanished. The loss recurs until the king demands an explanation.
The advisers say a child born without a father must be found, killed and used to consecrate the foundations with blood. Messengers search and discover a boy whose parentage becomes the subject of a quarrel between children. He is brought before Vortigern for a purpose he has not chosen. The narrative’s central reversal begins when the intended victim starts asking the questions.
The boy makes the advisers show their knowledge
Instead of accepting the explanation, the child asks what lies below the building place. The wise men cannot answer. He directs an excavation, revealing a pool, then concealed containers and a folded covering. Two sleeping serpents—one red and one white—are discovered within it.
The creatures begin to struggle. The white one first appears stronger and repeatedly drives the red back. The red then recovers, pursues its opponent and expels it. The child interprets their conflict in terms of peoples and kingdoms: the red belongs to Vortigern’s people, the white to the invading Saxons. The king’s immediate building problem opens into a prophecy about Britain.
In this text the child names himself Ambrose, and the story links him to Roman parentage. Later retellings commonly identify the boy with Merlin or Myrddin Emrys. Keeping the names attached to their respective versions shows how a famous character and a famous place became intertwined over time.
Lludd explains how the dragons came to be hidden
The story of Lludd and Llevelys in Lady Charlotte Guest’s Mabinogion translation supplies another strand. Britain suffers several plagues, including a terrible cry. Llevelys explains that two dragons are fighting and tells Lludd how to exhaust and capture them using a pit, a covering and a cauldron filled with mead.
Lludd measures the island and places the trap at its centre, identified in the tale as Oxford. The fighting creatures change form, tire, fall upon the covering and sink into the drink. Once asleep, they can be wrapped and removed. Lludd carries them to his most secure place in Snowdon and hides them in a stone chest.
Guest’s text names that hiding place Dinas Emreis, previously Dinas Ffaraon. The capture story and the Vortigern story can therefore be read together as burial and later disturbance. The setting in the north Welsh hills becomes the place where an older danger has been restrained, waiting beneath a ruler’s new foundations.
A real hill with walls and a tower
Dinas Emrys is also a physical place above the Nant Gwynant valley near Beddgelert. The National Trust’s description identifies the remains of defensive ramparts and a square tower at the summit. Its route through the surrounding woodland places the legend within a landscape visitors can still recognise.
The visible remains have their own architectural history. A medieval narrative can explain a place’s name or significance while walls and occupation evidence belong to different building phases. The attractive connection is the long use of a prominent defensive hill and the stories told about what lay within it. The photograph shows the hill from the Sygun side, not a staged picture of the dragons.
A contest over who can interpret the hidden world
Both medieval narratives turn on knowledge which a ruler lacks. Vortigern’s experts offer an explanation which threatens a child; the child answers with a sequence of discoveries. Lludd is powerful but needs his brother’s advice before he can deal with the dragon cry. Authority alone is insufficient until the hidden cause is understood.
The objects and actions are unusually concrete: foundations, a pool, folded cloth, a stone chest, drink and sleep. They give a shape to dangers which first appear only as loss or sound. In each story, handling the creatures changes the condition of a much larger territory. Dinas Emrys connects a small place in the hills with the fate imagined for a whole country.
Following the versions without losing the place
The early text’s Ambrose, later Merlin traditions and the Lludd story are related strands, rather than one unchanging eyewitness narrative. Reading the actual passages preserves differences in names, discoveries and outcomes. It also explains why modern accounts can begin at different points—Vortigern’s failed fortress, Lludd’s cry, or the symbolism of the red dragon—and still arrive at the same hill.
The pin marks Dinas Emrys itself. The official route and site information are linked for anyone researching the landscape; access arrangements should be checked there when planning a visit. For the historical library, the case offers a detailed chain from medieval texts to a recognisable Welsh setting, with the dragons retained in the form their stories give them.
Timeline
Early medieval literary tradition — Vortigern and the child are described in Historia Brittonum.
Medieval Welsh tale — Lludd and Llevelys explains the dragon cry and their concealment at Dinas Emreis.
Nineteenth century — Lady Charlotte Guest’s translation brings the Welsh tale to a wide English-reading audience.
Present landscape — ramparts and a square tower remain on the hill identified with the traditions.
Sources and further reading
Historia Brittonum, sections 40–42, translated by J. A. Giles
Public-domain translation of the failed building, the child, the pool and the red and white serpents.
Lady Charlotte Guest, The Mabinogion, “The Story of Lludd and Llevelys”
Public-domain translation of the dragon cry, mead trap and concealment at Dinas Emreis.
National Trust, The legendary trail of Dinas Emrys
Physical setting, surviving summit remains and current route information.
Location note
Hillfort location associated with the medieval traditions. The pin represents the site, not a precise underground chamber.
Map location source · Checked 4 November 2026.
Related cases
The Green Children of Woolpit: two medieval accounts and the road from St Martin’s Land
The Lady of Llyn y Fan Fach: the three blows, the returning cattle and the physicians of Myddfai