Ancient Monuments

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Carneddau Hengwm Long Cairns

A Scheduled Monument in Dyffryn Ardudwy, Gwynedd

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Latitude: 52.7647 / 52°45'52"N

Longitude: -4.0566 / 4°3'23"W

OS Eastings: 261331

OS Northings: 320549

OS Grid: SH613205

Mapcode National: GBR 5S.YYY1

Mapcode Global: WH56D.NRHW

Entry Name: Carneddau Hengwm Long Cairns

Scheduled Date:

Source: Cadw

Source ID: 2454

Cadw Legacy ID: ME007

Schedule Class: Religious, Ritual and Funerary

Category: Chambered long cairn

Period: Prehistoric

County: Gwynedd

Community: Dyffryn Ardudwy

Traditional County: Merionethshire


The monument consists of the remains of two chambered long cairns, dating to early Neolithic (c. 4,200BC - 3,000BC). A long cairn is a roughly rectangular or trapezoidal mound of stone, usually between 25m and 120m long, with a length exceeding twice its greatest width. The mound may be edged with a timber or stone revetment, and they contain one or more stone or wooden burial chambers at one end.


A long cairn which is aligned on a northwest to southeast axis and measures 56m in length and is 20m in width, the scattering of stones at the site suggest that the original cairn was probably smaller. At the eastern end of the cairn are the remains of a portal dolmen which consists of three upright slabs with an average width of 1.4m and the tallest of which is 2.2m in height. There are two large slabs lying on the ground west of the uprights which could be capstones. A second chamber in the cairn lies some 22m west of the portal dolmen and is built of drystone walling, with a capstone covering the top. Drystone walling between the two chambers is visible within the cairn material and occurs 8m west of a modern field wall which crosses the cairn. It is visible for a length of 3m and height of 1.3m.


The smaller northern cairn has the same alignment as its neighbour and measures 30.5m in length and is 15 in width. The cairn material is much denuded and thus it is not possible to state the exact dimension of the original structure. One large slab which measures 3.6m in length and 2.75m in width lies on the bed of cairn material towards its western end , probably a capstone remains Almost at the centre of the cairn can be seen the ruined walls of a roughly circular chamber of dry built masonry having a diameter of c. 3m. Some 4.6m east of the circular chamber are five slabs of stone set on edge, which indicate the former presence of two long, narrow rectangular chambers c.0.9m wide set across the cairn, one on each side of its axis. An interesting feature of the monument is the existence of straight lines of dry built stone walling down the sides of the cairn, not parallel but converging slightly towards the west. They are built of flat slabs of slate type stone, quite distinct from the rest of the cairn material. The line of these revetment walls can be traced also at the west end of the cairn, although part of the face has recently been destroyed on the south side.

The monument is of national importance for its potential to enhance our knowledge of prehistoric burial and ritual practices. The features are an important relic of a prehistoric funerary and ritual landscape, together with environmental and structural evidence. Chambered long cairns may be part of a larger cluster of monuments and their importance can further enhanced by their group value.

The scheduled area comprises the remains described and areas around them.

Source: Cadw

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