Pollen dating archaeology
On the island of Öland, Sweden, nineteen ringforts have been identified, including Eketorp, a site that has been completely excavated and that one may visit.
Currently, excavations are ongoing at Sandby borg, which was the site of a massacre in the 5th Century A. It is also possible that the Hill of Tara is an early type of ringfort.
They might have served as boot camps for Sweyn Forkbeard's men before his invasion of England in 1013.
The debate on chronology is primarily a result of the huge number of ringforts and the failure of any other form of settlement site to survive to modern times in any great quantity from the period before the Early Christian period or from Gaelic Ireland after the Anglo-Norman arrival.
While conceding that most ringforts were built in the Early Christian period, he suggests a link between the arrival of Eóganachta dynasty in Munster c.400 AD, and the introduction of ringforts.
In support of this he notes that: "The other major Eoganachta ringforts [other than Cashel] of Ballycatten, Garranes and possibly Garryduff, despite limited stratigraphic discernment, have produced artefacts of ambiguously early origins. supports an intrusion of a Celtic warrior caste..." The similarity with South Welsh 'raths' and Cornish 'rounds' suggests a degree of cultural interaction between Western British and Irish populations, however differences in dates of occupation mean this cannot be confirmed.
is based on the absence of any other settlement form of appropriate date in those landscapes.
In other words, if the Gaelic-Irish did not live in ringforts, where did they live?
If one were to accept a defensive function for ringforts, it would seem that after the introduction of more complex forms of defensive structures into Ireland this would naturally lead to the use of ringforts and raised raths in a manner analogous to the contemporary Norman buildings.
From a morphological viewpoint, and probably also from the view of the contemporary person, there is little to distinguish a ringfort from a small earthwork castle or motte.
Indeed, in a number of cases it would appear that either the Normans converted existing ringforts into the basis of the future construction of mottes and earthworks, or that the Gaelic Irish, through the use of raised raths, sought to emulate the Norman example.
However, many hitherto unknown ringforts have been found thanks to early Ordnance Survey maps, aerial photography, and the archaeological work that has accompanied road-building.
In Cornwall There are seven known ring fortresses in Denmark and southern Sweden, all from around 980 in the Viking Age.