Ancient Monuments

History on the Ground

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Caer y Twr

A Scheduled Monument in Holyhead (Caergybi), Isle of Anglesey (Ynys Môn)

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Latitude: 53.3132 / 53°18'47"N

Longitude: -4.6748 / 4°40'29"W

OS Eastings: 221904

OS Northings: 382918

OS Grid: SH219829

Mapcode National: GBR GMTY.CDX

Mapcode Global: WH314.5Z5F

Entry Name: Caer y Twr

Scheduled Date:

Source: Cadw

Source ID: 2509

Cadw Legacy ID: AN019

Schedule Class: Defence

Category: Hillfort

Period: Prehistoric

County: Isle of Anglesey (Ynys Môn)

Community: Holyhead (Caergybi)

Built-Up Area: Holyhead

Traditional County: Anglesey


Caer y Twr comprises an Iron Age hillfort situated on the top of Holyhead Mountain. It is defended by a strong 3 m thick dry-stone wall enclosing some 17 acres. The wall runs round the north and east sides of the fort; the south and west sides are naturally protected by steep cliffs. The wall has not survived so well on the north west side, but on the north and east sides it survives in places to a height of nearly 3m. It has been suggested that a rampart walk was a feature of the wall, but there is less evidence for this now.

On the north east side of the fort is a simple inturned entrance, about 3m wide, which makes use of a natural gully. The interior of the fort is rough and rocky, with no sign of any contemporary habitation sites. However, recent excavation has revealed the possible remains of a Roman signal station on the summit, adjacent to the Ordnance Survey trig point.

There has recently been fairly extensive refurbishment of the footpaths, including repairs, the creation of rough steps, and the piling of stone to discourage use of alternative routes.

This monument is of national importance for its potential to enhance our knowledge of prehistoric domestic life, social organisation and defensive practices. The scheduled area comprises the remains described and an area around them within which related evidence may be expected to survive.

Source: Cadw

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