SMR No.: DG047-012001-
Monument Type: Ringfort - cashel
The site generally referred to as the 'Grianán of Aileach' (National Monument number 140) consists of a restored cashel centrally placed within a series of three enclosing earthen banks (DG047-012005-), the site of a 'tumulus', the site of an approaching 'ancient road' and a holy well.
The cashel was surveyed and described by Petrie in 1835 (Colby 1837, 217-232). It subsequently fell into a state of considerable disarray but was rebuilt and restored between 1874 and 1878 by Dr. Walter Bernard of Derry (Bernard 1870-9, 415--23). The internal diameters of the cashel are 23.6m N-S and 23.2m E-W. A lintel-covered entrance-passage, 4.65m long, 1.12m wide and 1.86m high leads into the interior from the E. Slight recesses, situated on each side of this entrance-passage, have been filled in but not obscured. The interior rises in three terraces, accessible by inset stairways to a height of c. 5m. On the outside the wall is gracefully battered with dry-stone construction. Two wall-passages, one from the S and another from the NE run towards but stop short of the entrance-passage. The S wall-passage entrance is .45m wide, .6m high and 1.4m long. It turns through a right-angle where it becomes .5m wide, .85m high and 20.4m long. Near the N end there is a recess on the W side .5m wide. 1m high and 0.75m deep. The NE wall-passage entrance is .65m wide, .97m high and 1.55m long. It meets the main part of the passage in a T-junction. To the N the passage is .7m wide, 1.3m high and 2.5m long. To the S the passage is .6m wide, 1.4m high and 8.6m long. At the end of the passage there is a seat-stone across its full width. The interior of the cashel is fairly level but Petrie recorded traces of a rectangular stone structure at the centre, which he believed to be the remains of a 'chapel' (DG047-012007-) dating to the Penal period (18th century). A drain runs through the cashel wall at ground level on the NW side. Dr. Bernard recorded the finding of midden material and stone objects inside the cashel during his reconstruction work.
The innermost external bank is at a distance of c. 25m from the cashel wall. It is very low, worn and heather-covered but traceable for almost its entire circuit. A gap to the ENE gave onto the 'ancient road' (DG047-012004-) which approached the summit of the hill between two natural ledges of rock outcrop. Petrie's plan of the site shows the distance between this gap and the cashel entrance lined by settings of stones. There are possible indications of a fosse on the external side of the bank.
Midway between the inner and middle banks and SE of the cashel entrance is a low mound of broken stones (DG047-012002-). This is possibly the remains of the 'tumulus' shown roughly in this position on Petrie's plan.
The middle and outer banks exploit the contours of the top of the hill at varying distances from each other and from the cashel. The middle bank encloses an area of 4 acres (1.6 hectares). Like the inner bank, the middle and outer banks are much worn away and heather-covered. For long stretches they are untraceable, particularly the outer bank. There are slight indications, in places, of a fosse on the internal side of the middle bank and possibly indications of another fosse in places between the two banks but turf-cutting and general erosion make it difficult to be certain. While some stone is visible in the banks they are predominantly of earthen construction.
Between the two outer banks on the S side of the hill there is a spring well (DG047-012003-) dedicated to St. Patrick (Ó Muirgheasa No.88). It is likely that this 'is a multi-period site. The 'tumulus' could well have been dated to the Neolithic period or the Bronze Age. The earthen enclosures are usually interpreted as a hillfort of the Late Bronze Age or Iron Age (Raftery 1972, 37-58). The cashel clearly belongs to the early historic period. Although a site in the nearby townland of Elaghmore (now inside the boundary of County Derry) is sometimes put forward as the site of Aileach, the ancient seat of the northern Ui Neill, most writers have identified the monuments described above as the location of that important settlement. There is much legendary and historical material associated with Aileach and the Irish annals record its destruction in 1101. The Grianán of Aileach is situated in rough terrain on the summit of a hill looking N across the former marshy area which separates Inishowen from the rest of Donegal. It commands extensive views along Lough Swilly and Lough Foyle and much of the surrounding area in Counties Derry, Donegal and Tyrone and in turn it can be seen from a very wide area. It is located about 7 miles (11.25 kilometers) NW of the important early ecclesiastical site at Derry with which its history is closely linked.
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High Resolution Data
3D Capture Method: Terrestrial laser scanning (TLS)
3D Capture Description: Phase based terrestrial laser scanning using a Faro Focus 120 laser scanner. The instrument quotes the following specification:
- Distance accuracy up to ±2mm.
- Range from 0.6m up to 120m.
- Measurement rate up to 976,000 points/sec.
- Intensity & RGB. Integrated colour camera.
- Photorealistic 3D colour scans with up to 70 megapixels.
- Parallax-free colour overlay.
Laser scans geo-referenced using RTK GPS with VRSnow corrections
Data Processing Software
Processing of point cloud data: Faro Scene & Pointools
Meshing of data: Geomagic Studio 2012
3D Modelling & Texturing: Autodesk Mudbox, Mari, 3D Studio Max