Ancient Monuments

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Castell Odo

A Scheduled Monument in Aberdaron, Gwynedd

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Latitude: 52.8232 / 52°49'23"N

Longitude: -4.692 / 4°41'31"W

OS Eastings: 218709

OS Northings: 328472

OS Grid: SH187284

Mapcode National: GBR GPS7.HHG

Mapcode Global: WH33M.W9WH

Entry Name: Castell Odo

Scheduled Date:

Source: Cadw

Source ID: 293

Cadw Legacy ID: CN045

Schedule Class: Defence

Category: Hillfort

Period: Prehistoric

County: Gwynedd

Community: Aberdaron

Traditional County: Caernarfonshire


The monument comprises the remains of a hillfort, which probably dates to the Iron Age period (c. 800 BC - AD 74, the Roman conquest of Wales). The earthworks surround the low summit of Mynydd Ystum and consist of outer and inner defensive banks that enclose an area approximately 50m in diameter with an entrance through the inner bank is on the north east. The outer bank is 4m wide, about 1m high on the west where it is best preserved but spread to twice this width and only just discernable on the east. On the south and east it is grass covered but elsewhere has bracken and gorse. Between the outer and inner banks on the west is a single possibly orthostatic boulder 0.5m high. The inner bank is graded into the slope on the outside for much of its circumference and is best preserved on the west; it averages about 0.5m high from the interior. In the enclosure there are a series of hut circles which are described clockwise from the entrance:

(a)Set against the inner bank adjacent to the entrance, sub-circular with internal dimensions 4.5m E to W and 6.5m N to S, the entrance is on the NW. The wall is a low earth and stone bank covered in turf, bracken and gorse 1m wide and c. 0.1m high on the exterior. The floor of the hut is sunk approx. 0.5 to 0.6m below the height of the wall.

(b)Circular and about 6.5m diameter set near to and 0.3m below the rise of the inner bank on the south and showing as a low earth bank c. 0.1m high and 1m wide with a slightly sunken interior; grass-covered.

(c) North west of (b) with its entrance south east, 6m internal diameter, the wall is best preserved on the west and north (adjacent to the pillow mound – see below) and there 0.5m high with some stone discernible under turf.

(d) Against the west bank, a level rectangular area 6m N to S and 3-4m wide with a low turf wall along the inner bank 1m wide and 0.2m high looping around to the north west and also visible turning at right angles from the south corner.

(e) Circular with an internal diameter of 6m and a wall 0.2m high and 1m wide merging into the bank on the west side, no apparent entrance. Turf and bracken covered.

(f) East of (e) and slightly upslope, the wall is 0.2m high and 1m wide and surrounds a sunken interior 0.5m below the ground level and 6m in diameter, in the centre of which is a mound 3m diameter with a central 1m diameter hollow

(g) Adjacent to the north side of the entrance with a floor 5.5m in diameter and walls 1m wide and 0.1m high, the entrance is to the east next to the in-turn of the bank, grass-covered. On the south side of the interior is a pillow mound about 15m long NNW to SSE and 3m wide.

The monument is of national importance for its potential to enhance our knowledge of later prehistoric defensive organisation and settlement. The site forms an important element within the wider later prehistoric context and within the surrounding landscape. The site is well preserved and retains considerable archaeological potential. There is a strong probability of the presence of evidence relating to chronology, building techniques and functional detail.

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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