The Brú na Bóinne passage grave sites continue to surprise archaeologists, with two large enclosures discovered near Knowth. The formation of one of them is unique in Ireland, leaving researchers mystified about how it might have been used.
     The two buried features were found in a field adjacent to Knowth, no more than 40 or 50m from the famous passage tombs there, according to Joe Fenwick of NUI Galway. "The place where we were surveying is very near the core area where most of the tourists visit," he said. There were virtually no bumps or irregularities at the surface, yet his collaborator, Prof George Eogan of University College Dublin - who has conducted research at Knowth for 50 years - felt there was potential there because of earlier aerial surveys.
     Mr Fenwick probed below the surface using a magnetometer, a device that detects changes in the natural magnetism of the soil caused by ground disturbance. He described his shock when not one but two large hidden features emerged. One is a large rectangular enclosure, in effect a soil platform 65m wide and of an as yet uncertain length. This is surrounded by a wide ditch of about 15 metres across. The second - an enclosure made of two concentric rings - was unknown in Ireland, he said. The outer is 70m across and has a surrounding 3-4m ditch. The inner ring has its own ditch around it and is 25-30m across.
     "The ring enclosure was completely unexpected because there were no signs of it on the surface," he said. "It is fantastically exciting. It is difficult to come up with a parallel for it. There is a possibility it could be a ring fort but it doesn't match others." The features may date back to the 12th or 13th century. The survey also revealed what may be walls built on the platform. "It was a major piece of construction. It was not built for farming activity."
     These discoveries convince Mr Fenwick that there are many discoveries yet to be made. "The scale of Knowth is much, much bigger than anyone realised. The potential for further discoveries around Knowth is enormous." Knowth, along with the nearby Newgrange and Dowth passage graves, are between 5,000 and 5,200 years old and are collectively a World Heritage Site.

Edited from The Irish Times (23 November 2011)