The Aran Islands are strategically located across the mouth of Galway Bay and geologically they are outliers of the main Burren limestone plateau. There are seven large stone forts on the islands and most of the fieldwork associated with the Western Stone Fort Project has been concentrated on this unique 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 sovereignity over the seaways. 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.