Eryri Through Time

From Fire and Ice to Slate Quarries

Rising above the valleys of north-west Wales, Eryri is one of the most recognisable landscapes in Britain. Its jagged peaks, deep glacial valleys, tranquil lakes and sweeping moorlands have inspired poets, challenged climbers and attracted millions of visitors, but these mountains are far more than spectacular scenery. For thousands of years, they have shaped the lives of the people who called them home.

Every landscape has a story, and few are as remarkable as that of Eryri. Long before castles crowned rocky outcrops or slate quarries echoed with the sound of industry, immense volcanoes built these mountains, while vast glaciers carved them into the dramatic landscape we see today. Those same mountains later provided shelter for prehistoric communities, formed the heartland of the Kingdom of Gwynedd, protected the last independent Welsh princes, sustained isolated farming communities, and eventually supplied the slate that roofed cities around the world.

The story of Eryri is therefore not simply one of natural beauty, but of the close relationship between people and place. Each generation inherited the same landscape, adapting it to meet their own needs while leaving behind traces of their lives for future generations to discover. In this article, we'll uncover those traces as we follow Eryri through the six ages of Welsh history.

How Fire and Ice Created the Mountains of Eryri

The story of Eryri began around 450 million years ago during the Ordovician Period, when most of Wales lay beneath a warm tropical sea south of the Equator. While much of the country was covered by layers of mud and sand settling on the seabed, north-west Wales lay within an active volcanic province. Here, repeated eruptions built up immense thicknesses of volcanic ash and lava, creating a mass of hard volcanic rock far more resistant to erosion than the surrounding sedimentary rocks. It is largely because of this ancient volcanic landscape that Eryri stands as Wales' highest mountain range today.

As ancient continents collided during the Caledonian Orogeny, these rocks were compressed, folded and faulted, raising the mountains that would eventually become Eryri. The immense heat and pressure transformed many of the mudstones into slate, while mineral-rich fluids deposited veins of copper, lead and other metals within fractures in the rock. These natural resources would shape the region's future just as much as its mountains.

The landscape seen today, however, owes as much to ice as it does to fire. During the last Ice Age, vast glaciers flowed through the mountains, widening existing valleys and carving dramatic new landforms. They created the broad U-shaped valleys of Llanberis and Nant Gwynant, hollowed out corries such as Cwm Idwal, sharpened the narrow ridge of Crib Goch, and left behind the countless lakes that still fill the mountain hollows.

As the ice retreated around 12,000 years ago, rivers such as the Glaslyn and Ogwen continued to shape the landscape, while peat slowly developed across the uplands. Grasses, shrubs and eventually woodlands spread across the valleys, providing habitats for wildlife that migrated into Wales as the climate warmed. Red deer, wild boar, wolves and brown bears roamed the forests, while rare Arctic-alpine plants, including the Snowdon lily and purple saxifrage, survived on the highest slopes. Peregrine falcons nested among the cliffs, and choughs foraged across the windswept mountainsides.

Crib Goch's razor-sharp arête was carved by glaciers on either side of the ridge.

Llyn Idwal beneath the towering cliffs of one of Britain's finest glacial corries.

Ice Age reconstruction showing how a glacier carved Cwm Idwal into a classic corrie.

Plucking and abrasion at the glacier's base carved the bedrock beneath Cwm Idwal.

Glacial striations reveal the direction of ice flow across polished bedrock.

How glaciers carved a corrie through plucking, abrasion and thousands of years of ice.

The classic features of a glacial corrie clearly visible around Llyn Idwal.

The First People of the Mountains

As the climate continued to warm after the last Ice Age, Eryri's valleys became increasingly rich in woodland and wildlife. Around 10,000 years ago, Mesolithic hunter-gatherers followed herds of red deer and other game into the mountains, travelling along rivers and through forested valleys in search of food. Small flint tools discovered around Eryri's valley floors and lake margins suggest that these early communities established temporary camps as they moved seasonally through the landscape, exploiting its rich natural resources. Pollen records also indicate that Mesolithic people deliberately burned patches of woodland to create clearings that attracted grazing animals such as red deer. Although they left few permanent traces, their seasonal journeys marked the beginning of humanity's long relationship with the mountains.

By the Neolithic period, around 6,000 years ago, farming had reached Wales. Although Eryri's steep mountain slopes were poorly suited to cultivation, the surrounding valleys and coastal fringes offered fertile land for crops and livestock. Archaeological evidence from the Glaslyn Valley, Dyffryn Nantlle and the Trawsfynydd area reveals early field systems, flint tools and settlement evidence, while pollen records show that forests were gradually cleared to make way for farmland. Around the edges of Eryri, communities also began constructing substantial stone burial monuments. The chambered tombs at Bachwen near Clynnog Fawr, Capel Garmon near Betws-y-Coed, and Dyffryn Ardudwy on the southern fringe of the mountains were built as communal burial places, where successive generations were laid to rest and ceremonies honouring ancestors are thought to have taken place. These monuments were concentrated around the mountain fringes, where people lived and farmed, suggesting that farming communities were becoming increasingly connected to particular places and their ancestors.

During the Bronze Age, from around 2500 BC, Eryri's mountains became an increasingly important part of everyday life as communities expanded onto the uplands to graze livestock, travel across mountain passes and leave their mark upon the landscape. The widespread use of bronze tools, weapons and ornaments depended upon copper, but although extensive prehistoric mining was taking place nearby at the Great Orme, there is no clear evidence that the copper deposits exposed around Nant Gwynant, Lliwedd and Beddgelert were exploited until later centuries. Instead, Eryri became one of Wales' great ceremonial landscapes, with hundreds of burial cairns constructed on prominent summits including Moel Siabod, Moel Eilio and Carnedd Llywelyn, while standing stones, occasional stone circles, roundhouses and field systems appeared across areas such as Trawsfynydd and Dyffryn Nantlle. Together, these remains reveal that Eryri had become far more than a place to hunt or farm; it was now a landscape where communities lived, buried their dead and expressed their beliefs.

By the Iron Age, from around 800 BC, Eryri had become home to permanent farming communities living in stone roundhouses surrounded by enclosed fields and grazing land. Earlier Bronze Age field systems continued in use, while settlements expanded across areas including Trawsfynydd, Dyffryn Nantlle and the Llanberis Pass. Defended hillforts also appeared at strategic locations such as Dinas Emrys near Beddgelert, Craig y Dinas near Dolwyddelan and Braich y Ddinas above Penmaenmawr, controlling routes through the mountains and along the coast. Beads, stone querns and pottery show that goods were arriving in Eryri from other parts of Wales and beyond, demonstrating that these communities formed part of a wider trading network. While there is no direct evidence for what was being exported, sheep and cattle bones suggest that livestock farming underpinned the local economy, making it likely that wool, hides and livestock were exchanged for incoming goods.

For centuries, these isolated mountains also inspired many of Eryri's enduring legends. Among the best known were the Gwyllion, mysterious female spirits said to haunt lonely mountain paths and mist-covered passes, reflecting both the dangers and mystery of travelling through Eryri's rugged landscape.

A cairn marks the route across Eryri's dramatic mountain landscape.

Capel Garmon Chambered Tomb as it appears today.

Neolithic communities building Capel Garmon Chambered Tomb.

Reconstruction of Capel Garmon Chambered Tomb around 5,000 years ago.

Communal burial ceremony inside the Neolithic tomb.

The tomb stood prominently above the surrounding landscape.

Eryri and the Birth of the Kingdom of Gwynedd

The Roman conquest of north Wales reached Eryri during the first century AD as the Roman army campaigned against the Ordovices. Rather than establishing towns deep within the mountains, the Romans controlled the region from forts such as Segontium at Caernarfon and Canovium in the Conwy Valley, while roads and smaller military sites secured the main routes around the mountain massif. Eryri itself remained a sparsely populated upland landscape where native farming communities continued to live much as they had before the conquest. However, by the end of Roman rule in the early fifth century, many of Eryri's Iron Age hillforts had been abandoned for centuries as Roman authority replaced the local rulers who had occupied them.

Following the Roman withdrawal, political power passed from imperial governors back to local rulers. According to later tradition, Cunedda and his followers migrated from northern Britain to north Wales, establishing what would become the Kingdom of Gwynedd, although whether this tradition records a single migration or a longer process of settlement remains uncertain. By the sixth century, under rulers such as Maelgwn Gwynedd, the kingdom had become one of the most powerful in post-Roman Britain, with Eryri forming its secure mountainous heartland.

Eryri's landscape gave the young kingdom a considerable advantage. Rugged mountains, narrow passes and secluded valleys created natural defences against invasion, while the fertile coastal plains of Arfon and the shores of the Menai Strait provided productive farmland and easy access to the Irish Sea. Control of routes through passes such as Llanberis and Nant Gwynant allowed Gwynedd's rulers to move men and supplies while denying easy access to their enemies. These natural advantages helped establish Eryri as both a refuge in times of conflict and the strategic centre from which the kingdom could flourish.

Some of these long-abandoned hillforts now found a new purpose. The Iron Age stronghold at Dinas Emrys near Beddgelert was reoccupied, with stone buildings and imported Mediterranean pottery indicating that it had become an important high-status centre. Its commanding position overlooking the Glaslyn Valley made it an ideal refuge during a time of political instability, while later Welsh tradition forever linked the site with the legends of Merlin and Vortigern.

Christianity also spread through the mountains during these centuries. Early religious communities were established at Llanberis and nearby Nant Peris, traditionally associated with Saint Peris, while Beddgelert developed around an early ecclesiastical site linked to Saint Celert.

Reconstruction of Dinas Emrys during the early medieval period.

Saint Peris travelling through the mountains of Eryri.

An early Christian church became the heart of the local community.

Early churches offered hospitality to travellers crossing Eryri.

Worship inside one of Eryri's earliest Christian churches.

St Peris' Church continues a Christian tradition over 1,400 years old.

St Peris' Church still stands at the heart of its community.

Mountains of the Princes

By the High Middle Ages, Eryri had become the great stronghold of the Princes of Gwynedd. Medieval chronicles describe the mountains as a place of refuge during times of war, where Welsh rulers could withdraw beyond the reach of invading armies before launching campaigns to reclaim their lands. This strategy was employed repeatedly throughout the thirteenth century. Following Edward I's invasion in 1277, Llywelyn ap Gruffudd retreated into the mountains after losing much of the surrounding lowlands, while his brother Dafydd made his final stand in Eryri before his capture near Nanhysglain in 1283. The narrow passes of Llanberis, Nant Gwynant and the Conwy Valley offered natural defences and became strategically important routes into the mountain heartland.

People strengthened these natural defences by building a network of fortresses across the mountain passes. The earlier stronghold at Dinas Emrys continued to overlook the Glaslyn Valley, where excavations have uncovered evidence of continued occupation throughout the medieval period, including stone buildings and a defensive tower built upon the ancient fortifications. At Dolbadarn Castle, built by Llywelyn ab Iorwerth above Llyn Padarn at the entrance to the Llanberis Pass, excavations have uncovered medieval pottery, iron arrowheads, horseshoes, knives and other domestic objects, showing that the castle served as both a military fortress and an occasional royal residence. Further south, Dolwyddelan Castle guarded the approaches through the Lledr Valley, completing a network of fortifications that protected the mountain kingdom.

Life continued beyond the castles. Archaeology reveals how the stone roundhouses of earlier periods gradually gave way to traditional Welsh longhouses, the remains of which survive in valleys including Nant Gwynant, Nant Peris, Cwm Pennant and Hafod y Llan. Built of local stone with people living at one end and livestock sheltered at the other, these farmhouses were ideally suited to Eryri's pastoral landscape. Cultivation terraces, sheep folds and abandoned farmsteads reveal generations of mountain farming, while the seasonal movement of livestock between permanent hendre farms in the valleys and upland hafod settlements made full use of the region's varied terrain.

The early Christian communities founded during the Dark Ages also evolved into medieval stone churches at Llanberis, Nant Peris and Beddgelert, serving established parishes scattered among the mountains. 

Dolbadarn Castle under construction during Llywelyn the Great's reign.

Dolbadarn Castle guarded the gateway into the heart of Eryri.

Travellers passed beneath Dolbadarn Castle on the route into Eryri.

Cutaway showing the design of Dolbadarn Castle's round keep.

Owain Goch imprisoned inside Dolbadarn Castle's round tower.

Dolbadarn Castle still overlooks the Llanberis Pass today.

Dolwyddelan Castle guarded the eastern approaches to Gwynedd.

Dolbadarn formed part of Gwynedd's mountain defence network.

Life in the Mountain Communities

Following Edward I's conquest, the mountains that had once sheltered Welsh princes entered a very different age. The great castles of the Welsh princes lost their military importance as English rule became firmly established. Dolbadarn Castle was abandoned and gradually fell into ruin overlooking the Llanberis Pass, while Dolwyddelan remained garrisoned for a time before it too was deserted. Dinas Emrys also fell out of use as a defensive stronghold, surviving instead through the growing legends of Merlin and Vortigern that became attached to the ancient hill.

Life continued beneath the mountains. Archaeology shows that the traditional Welsh longhouses at Nant Gwynant, Nant Peris, Cwm Pennant and Hafod y Llan remained occupied, while cultivation terraces, sheep folds and abandoned farmsteads reveal a landscape devoted to pastoral farming. The seasonal movement of livestock between permanent hendre farms in the valleys and upland hafod settlements continued to make full use of Eryri's varied terrain, while packhorse routes carried wool, hides and other produce through the mountain passes to surrounding markets. Slate quarrying became increasingly organised during this period, as the incoming English lords built their manor houses, demand for durable roofing increased, encouraging the opening of small workings around Llanberis and the Nantlle Valley. Worked by hand and supplying mainly local markets, these modest quarries laid the foundations for the industry that would later transform Eryri's landscape.

The churches of Eryri also entered a new age. Though the medieval churches at Llanberis, Nant Peris and Beddgelert continued to serve scattered mountain communities, the Reformation brought profound change. Beddgelert Priory was dissolved in the sixteenth century, while Llanberis and Nant Peris saw religious images and shrines disappear, and their church interiors become plainer as worship followed the new Protestant traditions. Yet these churches remained at the centre of community life and, following the publication of William Morgan's Welsh Bible in 1588, played an important role in preserving the Welsh language among the people of Eryri.

A typical Tudor parish church in the mountains of Eryri.

The hendre was the family's permanent home in the valley.

Families drove livestock to the hafod each spring.

Families spent the summer months living and working at the hafod.

Many former hafodau still survive in the mountains of Eryri.

Hafod y Llan beneath the mountains of Eryri.

The annual cycle of transhumance in Tudor Wales.

Families travelled annually between the hendre and hafod.

The ruins of former hafodau still survive across Eryri.

The Slate Quarries that Changed Eryri

During the eighteenth and nineteenth centuries, the Industrial Revolution transformed Eryri from a landscape of scattered farms into one of Britain's most important mining districts. Rapid urban growth elsewhere created an enormous demand for durable roofing, while advances in engineering, transport and mining encouraged investors to exploit the region's rich slate and explore other mineral deposits on an unprecedented scale. Small workings around Llanberis and the Nantlle Valley expanded into vast industrial quarries, while copper mines at Sygun near Beddgelert and around Nant Gwynant and Lliwedd, together with the lead and zinc mines of the Gwydyr district near Betws-y-Coed, developed to exploit the mineral wealth created by Eryri's ancient volcanic past.

Archaeology reveals the extraordinary scale of this transformation. At Dinorwig Quarry above Llanberis, the mountainside was carved into immense stepped galleries linked by inclines, tramways, workshops, waterwheels and dressing sheds, while engine houses, barracks and hospitals served the thousands employed there. Similar remains survive throughout the Nantlle Valley, while abandoned copper and lead mines at Sygun and Gwydyr preserve adits, spoil heaps, dressing floors and engine houses that tell the story of Eryri's wider mining industry. Railways, improved roads and bridges connected these mountain industries with the coast, allowing Welsh slate and other minerals to be exported across Britain and around the world.

Historical records, maps, photographs and quarry accounts document the rapid growth of settlements such as Llanberis and Nant Peris, where scattered farming communities evolved into thriving industrial villages as thousands of quarrymen and miners came to work the mountains.

A vast industrial landscape grew beneath Dinorwig Quarry.

Entire communities grew around the slate industry.

The industrial heart of Dinorwig Quarry.

Quarrymen blasted huge blocks of slate from the mountainside.

Quarrymen split slate into durable roofing slates by hand.

Inclines and railways carried slate down the mountain.

Finished slates were exported from Port Dinorwig across the world.

The Slate Landscape of Northwest Wales became a UNESCO World Heritage Site.

Dinorwig Quarry still bears the scars of the Welsh slate industry.

Dinorwig Quarry transformed an entire mountainside.

Despite these dramatic changes, traces of every earlier age endured. Traditional farms continued to occupy the valleys, medieval churches remained at the heart of their communities, while prehistoric cairns, hillforts and castles still overlooked a landscape increasingly dominated by quarries and mines. Today, immense slate tips, abandoned workings, industrial railways and workers' settlements stand alongside monuments from every previous age, making Eryri one of the few places in Wales where over 450 million years of geological, archaeological and historical heritage can be explored within a single landscape.

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