Abergwyngregyn is a village of historical note in Gwynedd. It is located at grid reference SH653726, adjacent to the A55, five miles east of Bangor, eight miles west of Conwy.

History
Aber Garth Celyn, now known as Abergwyngregyn, and generally shortened to Aber, is a settlement of great antiquity and pre-conquest importance on the north coast of Gwynedd. Its boundaries stretch from the Menai Strait up to the headwaters of the Afon Goch and Afon Anafon. Protected to the east by the headland of Penmaenmawr, and at its rear by Snowdonia, it controlled the ancient crossing point of the Lafan Sands to Anglesey. A pre-Roman defensive enclosure, Maes y Gaer, which rises above Garth Celyn on the eastern side of the valley, has far reaching views over Irish Sea with the Isle of Man visible on a clear day. The Roman road from Chester, linking the forts of Canovium (later name Conovium) and Segontium, crossed the river at this point.

Garth Celyn
Garth Celyn is a strategic promontory of land overlooking the Menai Strait and the port of Llanfaes on the opposite shore. The Roman road that linked Conovium to Segontium (Caernarfon) looped round the Garth. At the end of the twelfth century, beginning of the thirteenth century, Llywelyn the Great utilized the promontory to build a royal home, known as Ty Hir, the Long House SH65827273 in later times. To the east was the newly endowed Cistercian monastery of Aberconwy; to the west the cathedral city of Bangor. Between Garth Celyn and the shore, the fertile farmland, provided food for the royal family and the members of the court. The sea and the river had fish in abundance and there was wild game to be hunted in the uplands. In 1211 King John of England brought an army across the River Conwy, and occupied the royal home for a brief period; his troops went on to burn Bangor. Llywelyn's wife, John's daughter Joan, negotiated between the two men, and John withdrew.

William de Braose, having been found in Llywelyn's chamber together with Joan, was hanged in the marshland below Garth Celyn, the place that was remembered as Gwern y Grog (Welsh: "Hanging Marsh"), in May 1230.

Joan died at Garth Celyn in 1237;

Dafydd ap Llywelyn died there in 1246;

Eleanor de Montfort, Lady of Wales, wife of Llywelyn ap Gruffudd, died there on 19 June 1282, giving birth to a baby, Gwenllian.

In November 1282, the Archbishop of Canterbury came to Garth Celyn to negotiate between King Edward and Tywysog Llywelyn.

In November 1282, Llywelyn wrote letters dated from Garth Celyn, totally recting the bribe offered by the Crown of England.

After the Conquest the name Garth Celyn was eliminated from the record books. The name, though it continued in local use, was never used in any document of the English administration.

The settlement Aber Garth Celyn adjacent to the royal home became officially known by the English conquerors simply as Aber, 'Estuary' with its identity removed; later more descriptively as Aber Gwyn Gregyn, 'Estuary of the White Shells'. The invasion of Wales was accompanied by savage reprisals against those who had stood in the way of the will of the king of England. On 18 January 1283, Dolwyddelan Castle was occupied by the army of invasion (PRO. E101/359/9)and immediately munitioned to provide a base in the Lledr valley. At Edward’s command raiding parties were sent out into the mountains of Snowdonia to search for booty. The troops were informed that they could claim one shilling as the king’s gift for the head of every Welshman that they brought back to camp.

Garth Celyn was surrounded and deliberately overshadowed by the castles of Conwy, Caernarfon and later Beaumaris. Wales became England’s first colony.

Pen y Bryn
Garth Celyn, the demesne messuage of the royal manor, became known as Pen y Bryn. In 1553 the 'Manor of Aber' was granted to the Thomas family; they converted the remains of Ty Hir, the medieval Long House, the home of the Princes, into an Elizabethan manor house. The tower, Twr Llywelyn, built c.1200, still stands.

Aber Valley
Aber Falls
The valley provides the access to one of Wales' great waterfalls, the Aber Falls as the Afon Goch falls precipitously, some 120 feet over a sill of igneous rock into a marshy area where it is joined by two tributaries; the enlarged stream, Afon Rhaeadr Fawr, heads towards the Menai Strait and the sea. Part way down it becomes Afon Aber Garth Celyn, or more recently Afon Aber, and the valley was known as Nant Aber Garth Celyn.

Bont Newydd
The single barrel-vault bridge at SH662720 spans Afon Aber Garth Celyn, providing a roadway across the river, some 25 ft in width. The date of construction is unknown, but its existence was marked on the O.S. map of 1822. The bridge provided a safe crossing for drovers leading animals up the valley. Large stones in the river under the bridge mark the site of an earlier ford.

Aber is the coastal crossing point for the ancient drovers and later Roman road that led across the Lafan Sands to Anglesey.

The Roman road from Chester crossed the River Conwy south of Tal-y-Cafn, connected with the fort at Conovium Caerhun by a short branch, then led up via Rowen and Bwlch-y-Ddeufaen, the Pass of the Two Stones, as an engineered overlay on top of the earlier British trackway, into Snowdonia.

The Roman road descends down Rhiwiau, the valley between Llanfairfechan and Aber, follows the coastal route west, loops round Bryn Llywelyn, Garth Celyn, crosses the river by means of a ford, passes by the church and leads on to the major Roman fort at Segontium, Caernarfon. The drovers road from Anglesey came into the settlement on the valley bottom on the west bank of the valley bottom , where provision was made for the animals to be penned and shod, and the feet of the geese to be coated in pitch, and then followed the valley to join with the Roman road.

Three Roman milestones have been discovered in the area. Two of these, found in 1883 in a field called Caegwag, on the farm Rhiwiau Uchaf SH6790727 are now in the British Museum, London.

Maes y Gaer
This is a defensive enclosure, built on a hill that forms the western end of a spur overlooking the valley at SH673725. It is approx 730 ft. above O.D. The walls of the enclosure are pair shaped and protect an area 400 ft long and 220 ft. wide of about one and a half acres. Maes y Gaer has a steep drop on all sides except the east, where the there is a more gentle slope leading to the pasture land. The entrance is on the south-east, now badly ruined but originally 11 ft. wide, with a passageway to the interior 20 ft. long. Below Maes y Gaer, above Garth Celyn Pen y Bryn, is a level area of land known as 'Elen's Garden' in memory of Eleanor de Montfort, princess of Wales.

Hafod Celyn, Hafod Garth Celyn
This is the summer pastureland of Garth Celyn, on open moorland rising to 800 ft above O.D. at SH676713. The small building on this site, now in ruins, was rebuilt in the eighteenth century on the ruins of an earlier building that extended further to the west.

Y Mŵd
"An earthen motte in the mouth of the valley marks the settlement and the prince's residence was set on a shelf just above it to the east". Dr Colin Gresham (T.C.H.S. 1979) The settlement of Aber Garth Celyn was on the valley bottom on the west bank of the river; the 'prince's residence' was on the 'shelf', Garth Celyn, to the east.

The precise nature of the 'earthen motte', Pen y Mŵd at SH656726, has led to much debate. It was renamed 'Aber Castle Mound' by the Ancient Monuments Board, on the grounds that 'it was assumed to be a Norman castle'. E. S. Armitage in her work The Early Norman Castles of the British Isles, confused Aber Garth Celyn with Aber Menai leading to the assumption that it might have been constructed by Hugh d'Avranches, earl of Chester. The word Mŵd in early Welsh means 'vault' or 'chamber', and there is no record or proof that the Normans, or anyone else, built a motte and bailey castle at Aber. The mound is circular, 22 foot high with an oval top 57 feet by 48 feet. It has been suggested that it might be a fifth or sixth century A.D. mound built over the body of a local champion warrior lord who in his lifetime had protected his people, and in death was expected to do the same. The area was Christian at this time, but the people still clung to their traditional beliefs. Other similar mounds have been found in western Britain, and while it is difficult to resolve the debate, it is worth mentioning.

Llyn Anafon
Llyn Anafon is the most northerly of the Carneddau lakes, lying between Llwytmor, Foel Fras and Y Drum. It has a maximum depth of 10 feet. A dam was built across the lake in 1930 to enable water to be supplied to the nearby coastal villages. There are brown trout in the lake and by long held custom people who lived in the village had the right to fish both the lake and the river. Half a mile below the lake there are pre-historic hut circles and other signs of early inhabitation.There is an arrow stone on the lower slopes of Foel Ganol, and another leading down to Cammarnaint Farm. A gold cross, five inches in height, was found on the summit of Carnedd y Ddelw above the lake in 1812.

The earliest name for the vale was Nant Mawan ('Record of Caernarfon', 1371, Bangor University Archives). Mawan being a personal name. The name contracted over time. Llyn Nant Mawan, became Llyn Nan (Mafon) and then Llyn (N)anafon.

Nearby is an area known as Buarth Merched Mafon (Enclosure of Mafon's Daughters).

Nothing is known about Mawan, but his son Llemenig is mentioned in several early Welsh sources. His name is mentioned in two englyns at the end of a 'Cynddylan' fragment in a manuscript (Canu Llywarch Hen XI. 112b.113b.)

When I hear the thundering roar, [it is] the host of Llemenig mab Mahawen [read Mawan]. Battle-hound of wrath, victorious in battle.

In Triad Ynys Prydain no. 43, his horse is described as one of the Three pack-Horses of Ynys Prydain. Ysgwyddfrith ('Dappled-shoulder') the horse of Llemenig ap Mawan.

Bird watching
Coedydd Aber is situated in an area of scenic beauty. The steep sided wooded valley, Nant Aber Garth Celyn, leads to the foothill of Y Carneddau. The river has the steepest fall of any in Wales and England. There is a wide variety of habitats in the valley including a diversity of woodlands, open farmland and scrub. A range birds can be found here, including raven, buzzards, peregrine falcon, sparrowhawk and choughs on the cliffs, tree pipit and redstart along the woodland edge, and pied flycatcher and wood warbler in the oak woods. By the shore, a hide has been erected on the edge of the Menai Strait, providing clear views of the sea birds on the Lafan sands. As a young man, Peter Scott, used Twr Llywelyn, the watchtower built c. 1200 on Garth Celyn, as a place to position his telescope, to watch the birds flying in off the Irish sea.

Glaciation
Since the beginning of the Ice Age, 2.4 million years ago, the uplands of North Wales have been subject to several phases of glaciation. The Aber valley provides physical evidence of the two younger phases of glaciation which occurred between 18,000-20,000 and 10,000-11,000 years ago. Y Carneddau has a notable range of glacial and periglacial features that have been studied by geologists, including Charles Darwin, for well over a century, and plays a key role not only into research into landforms, but also into climate change and vegetation history.