One of the best preserved Viking settlements in Europe has been discovered near the fishing village of Annagassan, in Co Louth.
It dates from 841, the same year Dublin was founded, and is believed to have been the previously unidentified fortress of Linnduchaill -- one of two chosen by the Vikings when they decided to winter in Ireland.
The other location was what would become Dublin.
The locals in Annagassan have always known there had been Viking links to the area but had no idea how big or important those connections were.
"Attempts to identify this site date back over 200 years and the significance of it is immense. It will be up there with all the major Viking sites in Europe," according to Eamonn Kelly, the keeper of antiquities with the National Museum who has taken a personal interest in the search.
He believes that Linnduchaill could have been "Dublin except (nearby) Dundalk Bay is shallow and access to it was determined by tidal conditions so Dublin won out".
The discovery of the fortress, which is located on a stretch of land between the coast and the river Glyde, is especially exciting for archaeologists as it is on agricultural land and as such is "completely preserved", he said.
The excavations, which began earlier this month, have so far uncovered part of a human skull, rivets used to build and repair ships, silver used for weighting and exchanging, a spindle whorl for spinning thread and a brooch pin.
The €30,000 given to the Annagassan and district historical society to carry out the archaeological digs came from the Louth leader partnership.
Film maker Ruth Cassidy, a member of the Annagassan historical society, said the group had walked up the river from its mouth and tried to think where they would have disembarked if they had been Vikings.
"This is where we came to," she said standing in a field which was once a centre of international trade and where the Vikings built and repaired ships.
The Louth county museum provided funding for a geophysical survey of the land and its results were so dramatic they were determined to secure more funding to dig the three trial trenches. "The geophysical readings showed massive archaeological activity and we knocked on every door but were denied funding to do the trial digs.
"Then the society applied to the Louth leadership partnership and they gave us the money and thank God they did," said Ruth.
The excavations, by professional archaeologists, began three weeks ago and on Wednesday there was no doubting they had come upon something extremely important.
As a result of the information revealed by the excavations, "we now know the extent and nature of the site for the very first time", said Mr Kelly.
So far a defensive rampart consisting of a ditch and bank have been found along with other indications it was a main fortress built by the Vikings.
The director of the excavations, Dr Mark Clinton, said, "In 841 the Vikings over-wintered for the first time instead of raiding and leaving. The annals said they over-wintered here and in Dublin and this location was elusive. Until now."
The site is believed to extend over a couple of square kilometres. Archaeologistswill evaluate what they have found at the location.