Ancient Monuments

History on the Ground

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Cross Ridge Dyke & Cairn on Twyn Hywel

A Scheduled Monument in Aber Valley (Cwm Aber), Caerphilly (Caerffili)

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Latitude: 51.6116 / 51°36'41"N

Longitude: -3.3001 / 3°18'0"W

OS Eastings: 310070

OS Northings: 191111

OS Grid: ST100911

Mapcode National: GBR HS.9LM7

Mapcode Global: VH6DK.RR6D

Entry Name: Cross Ridge Dyke & Cairn on Twyn Hywel

Scheduled Date: 10 February 1994

Source: Cadw

Source ID: 2917

Cadw Legacy ID: GM456

Schedule Class: Defence

Category: Cross Ridge Dyke

Period: Unknown

County: Caerphilly (Caerffili)

Community: Aber Valley (Cwm Aber)

Traditional County: Glamorgan


The monument comprises a linear bank and ditch running across an upland ridge. The tradition of cross ridge dyke building appears to roughly span a millennium, beginning in the middle Bronze Age and lasting throughout the Iron Age (although perhaps with reuse and perhaps limited construction in the medieval period). They have been interpreted as territorial boundaries, defining areas of political influence (including internal territorial boundaries and land allotment within communities) and perhaps have ritual associations.

The dyke on Twyn Hywel runs 440m across moorland. There is a central gap - the western half running south-west by north-east and ends on a slope and marshy area. The eastern half, runs east-west and ends to the east on a natural slope. Thirty metres north of the eastern half of the dyke is a small cairn. The dyke ditch lies to the north with the bank to the south. It measures approx. 3.4m across overall by about 0.5m high.

The monument is of national importance for its potential to enhance our knowledge of prehistoric land division and perhaps ritual practices. The monument is an important relic of a prehistoric landscape and retains significant archaeological potential, with a strong probability of the presence of environmental and structural evidence.

The scheduled area comprises the remains described and areas around them within which related evidence may be expected to survive.

Source: Cadw

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