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Cof Cymru: National Historic Assets of Wales · Wales

Relict Seawall alongside Collister Pill Reen

Magor with Undy, Monmouthshire, Wales

The record

Designation
Scheduled monument
Site type
Seawall
Period
Medieval
Date of designation
18 September 1995
Community
Magor with Undy
Unitary authority
Monmouthshire
Country
Wales
Coordinates (centre of the scheduled area)
51.57495, -2.80093
SAM number
MM226
Cadw record number
1420

Slide toward Today to fade the historical sheet and see the modern map underneath.

David Rumsey Map Collection, Stanford Libraries

Shown on 5 historical map sheets, the earliest the 1636 "Cornubia : Devonia, Somersetus, Dorcestria, Wiltonia, Glocestria ..." (David Rumsey Map Collection, Stanford Libraries).

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This record in Cadw's own full report ↗

Cadw's description

The following provides a general description of the Scheduled Ancient Monument.

The monument consists of a seawall running along the western side of Collister Pill Reen. This seawall was erected in the Middle Ages to enable the reclamation of the Gwent Levels in Undy parish and remained a sea defence until the enclosure of Caldicot Moor in 1850. The seawall is an earthen bank between 11m and 12m wide at the back and 5m wide on the top. It stands between 2m and 2.5m above the land to the west, but is almost level with the land on Caldicot Moor.

The monument is of national importance for its potential to enhance our knowledge of coastal defences. It retains significant archaeological potential, with a strong probability of the presence of associated archaeological features and deposits. The structure itself may be expected to contain archaeological information concerning chronology and building techniques.

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

Nearby in the register

Other entries of the same register within about three miles of this one, by straight line.

Designated Historic Asset GIS Data, The Welsh Historic Environment Service (Cadw), 2026-09-07, licensed under the Open Government Licence http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/ Cadw, the Welsh Historic Environment Service · Open Government Licence v3.0
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