Western Stone Forts Project

The Western Stone Fort Project examined in detail a group of large stone forts that are located in the west of Ireland. Around twenty-five of these forts have been identified and the best known examples are Dún Aonghasa on Inis Mór in the Aran Islands, Grianán Aileach in Co. Donegal and Staigue in Co. Kerry. Although, there are a large number of stone forts in Ireland, these twenty-five forts stand out because of their large size, or prominent location or because they have complex or massive defensive features.

The area enclosed at these forts varies from 14 acres at Dún Aonghasa to under half an acre at many of the smaller forts. Some forts may have as many as three enclosing walls; the inner wall is usually the most massive and examples up to 8.50m in thickness and over 4m in height are known.

Apart from their strong defences these forts share common architectural features, such as terracing of the walls, stone steps, and passages or chambers within the enclosing walls. Four forts have the unusual feature of a chevaux de frise – a band of closely set upright pillars of stone which formed an extra line of defence and which must have been a formidable obstacle for any potential attackers.

The research carried out by Claire Cotter and her team suggests that many of these forts are multiperiod sites and that what we see on the ground today is the result of remodelling and rebuilding over a long period of time. Like the cashels and ringforts that are common on the Irish landscape these forts were all occupied during the early medieval period (600-100AD) The stone fort at Grianán Aileach, for example, stands within a hillfort of prehistoric date. During the early medieval period the central stone fort was probably built and it was the royal seat of the Cenél Conaill (Northern Uí Néill).

The research carried out as part of this project has been published in the form of monographs (link to publications page here) and as a guide book to the Dún Aonghasa, a stone fort on the Aran Islands.

The Forts on the Aran Islands

The Aran Islands are located across the mouth of Galway Bay and there are seven large stone forts on the islands and most of the fieldwork for the Western Stone Fort Project has been focused on this group of spectacular forts. All seven forts were restored towards the end of the nineteenth century – photographs taken prior to the restoration indicate that the outer faces of the main enclosing walls were well preserved and survived to their present heights. The inner faces however were very dilapidated and in 1839 the interior of Dún Aonghasa was described as “a weird chaos of heaps and ruins”.

All seven forts were probably in use during the Early Medieval period (600 – 1000AD). Dún Eoghanachta, Dún Fearbhaí and possibly Dún Eochla were built at this time but Dún Aonghasa, Dúcathair and Dún Chonchúir were simply refurbished – the origins of these three forts goes back into prehistory.

The Early Medieval period was marked by political upheaval with many of the smaller kin-groups being pushed into the lower social orders by the rise of larger more powerful dynasties. The concentration of seven large forts on a relatively small land mass during the Early Medieval period may be largely due to the strategic location of the Aran Islands – historically they lay along the frontier between Connaught and Munster and were thus open to attack from both quarters. In addition the builders of the forts may have derived their wealth and power from their control of sea routes and trade. Apart from being an important source of food, the sea was the highway along which goods were transported – in the Early Medieval period these would have included commodities such as salt, wool, fish, meat, grain and iron ore.

Dún Aonghasa

The ground plan or architecture of an individual stone fort may give clues as to its date. In the case of Dún Aonghasa however theories as to its date varied widely. A programme of archaeological excavation was therefore carried out at the fort between 1992 and 1995. Initially, because of the thin soil cover on the hilltop, it was thought that very little archaeological evidence would have been preserved within the fort. This was not the case however and the excavation proved exciting and informative.

Dúcathair

This fort is located on the high cliffs along the southern side of Inis Mór; it consisted of a promontory which was defended on the landward side by a curved terraced wall and a chevaux de frise. The remains of conjoined stone houses can be seen in the interior; a series of long rectangular buildings built along the western edge of the promontory may have been cattle byres in a later period. There are a large number of promontory forts along the west coast of Ireland and this type of fort is generally considered to be of Iron Age date (200 BC – 500 AD). A small amount of pottery recovered from the site suggests that there may have been some settlement here predating the defences we see today. The integration of the conjoined stone houses with a broad low platform on the inner face of the enclosing wall also suggests that Dúcathair was occupied down into the Early Medieval period (circa 900AD).

Dún Eoghanachta

This small univallate fort stands on an inland cliff near the western end of Inis Mór. Limited archaeological excavations carried out here in 1995 suggest that the fort was built in the period 650 – 800AD. During this period, Arainn was renowned as a centre of ecclesiastical learning and attracted followers and pilgrims from far and wide. By patronising the early monasteries the wealthy inhabitants of Dún Eoghanachta no doubt reaped some economic benefit. In addition they may have exerised considerable control over the food supply and the provision of transport to and from the island.

Dún Eochla

This bivallate (double walled) fort stands near the highest point of Inis Mór. A concentration of other settlement sites (cashel, stone enclosures and house sites) occurs in the immediate vicinity. Without excavation it is not possible to say for certain when Dún Eochla was built. The remains visible today suggest that it belongs to the cashel class and this would place its construction sometime in the period 550 – 800AD. It is possible however that the present fort replaced an earlier mounment but again only excavation could ascertain this. No trace of any houses are evident today in the interior – the round structure may have been a signal station associated with the nearby lighthouse.

Dún Chonchúir

This spectacular fort can be seen from the sea as one approaches Inis Meáin – it lies about halfway along the island and overlooks a natural fault. The fort was defended by a massive inner wall, over 8m wide in places and which enclosed an area 70m by 40m. A slighter outer wall runs concentrically around all but the western side of the fort and a square forework projects from this on the northeast side. The western perimeter was protected by a rock cut ditch, the excavation of which probably provided much of the stone for the construction of the fort itself – 14,000 tons of stone were needed to build the inner wall alone.

The large size of the enclosure at Dún Chonchúir and its prominent and strategic location suggest that it is of prehistoric date. Only excavation could tell us for certain whether it was originally built during the Bronze Age or the Iron Age – like Dún Aonghasa it may have been rebuilt or remodelled on a number of occasions. A number of artefacts from the fort and the surviving house remains (some of square or rectangular plan) indicate that the fort continued to be occupied down into the Early Medieval period. The fort may have been slightly enlarged during this period – at the same time the inner wall was probably strengthened. The forework on the north-east side may have been built then or slightly later in order to protect the entrance.

Dún Fearbhaí

This univallate (single walled) fort is located at the eastern end of Inis Meáin and overlooks the modern harbour. Unlike the other stone forts on the islands it is roughly square in plan. This type of stone fort also occurs in the Burren and south Mayo and is generally considered to be a variant on the circular cashel. It is possible however that square forts may have appeared quite late in the development of cashels and not all may have been settlement sites. The interior of Dún Fearbhaí slopes down steeply – from the higher southern part of the interior it is possible to look out over the enclosing wall towards the harbour. This suggests that the fort was built to defend the harbour (and the island) from attack and it may also have protected a fleet anchored in the bay below. The fort is likely to have been built sometime between 700 – 900 AD.

Dún Formna

Located on high ground overlooking the harbour in Inis Oirr. This fort was modified in the Late Medieval Period when a tower house was built in the interior. The enclosing wall may also have been rebuilt at this time and the raised ground level in the interior may now partly overlie the foundations of an earlier thicker wall. It is not possible to date this fort by field examination alone as the later modifications now mask any earlier features.