Archaeologists believe they have found the remains of a huge Viking fortress near the village of Annagassan in Co Louth.
Three test trenches carried out on the site have revealed human remains, as well as the remains of 'hack' silver used for ship's ballast, nails for ship building and other artefacts of day-to-day life.
The test trenches have also revealed signs of a huge defensive wall, which would have protected the settlement on one side with the River Glyde and the Irish Sea protecting it on the other sides.
Archaeologists believe the site is that of Linn Duchaill, which was founded by the Vikings in 841 AD and which was a rival to the other large Viking town, Dublin.
According to the Ulster Annals, the Vikings used this base to raid inland as far as Longford and up to Armagh.
It is believed Linn Duchaill was a large trading town, exporting Irish slaves and looted goods.
There was also a large pitched battle there between the 'fair haired' Vikings and 'dark haired' Vikings in 851AD.
The site was last mentioned in the Ulster Annals in 927AD when it states that the Viking fleet left for Britain.
The discovery comes after years of work by local enthusiasts and members of the Annagassan and District Historical Society who always believed the area was the site of a large Viking settlement.
Several years ago they got funding from the Louth County Museum to carry out geophysical work on the site which showed the field as a likely candidate.
Now with funding from the Louth Leader Project, the test trenching has revealed these latest finds.
Those involved believe the find is of international significance and they hope the archaeological work will continue there for years.