The stone is a large, irregular shaped glacial erratic block of limestone of Lower Carboniferous around 250 million years old and is of local origin. It is probably part of a megalithic monument located at Seffin the exact site of which is now unknown.Known locally as the ‘Seefin Stone’ and mentioned by Geraldus Cambrensis in the 12th century, who referred to it as Umbilicus Hiberniae, ‘the Navel of Ireland’, it is said to mark the centre of Ireland. Archbishop James Usher (or Ussher), of Armagh (January 1581 – March 1656) & Primate of all Ireland says, that Birr was considered the centre of Ireland. He states that ‘it should have been remarked else where that long (perhaps a century) previous to the period now being treated of this town was reckoned to lie nearly in the centre of the Kingdom and it seems that there then was a large hollow stone somewhere here which used to be pointed out as that which Cambrensis in his Topographical Hibernia calls the Navel of Ireland’.Survey letters for the county argued that ‘Cambrensis was writing of Uisneach not Birr’.
Thomas Cooke described the stone as ‘a large limestone rock supposed to be the stone known in the days of Giraldus Cambrensis as the ‘navel of Ireland’. He goes onto state that ‘the place where it stood was not far from the town of Birr, and both places are in the parish of Birr. The Seffin rock stood on a little eminence beyond the present railway station, and at the same side of the road. This stone was a huge rude mass of limestone, marked with a number of incisions in the shape of fantastic crosses and other curious symbols, as usual, with stones of this description’ (Cooke 1875, 8). Local tradition claim that the indentations are from the hand of Fionn mac Cumhaill, hence the origin of the name as ‘Suigh Finn’ (pronounced ‘See-Finn’), the Seat of Finn. It was also reputed by oral tradition to have marked a meeting place of the Fianna.
Cooke states that ‘Seffin was spelled in old documents, Sheefin and Seefin, which seem to be composed of two Irish words, ‘Shee’, a spirit, and ‘Fen’ or ‘Phen’ identical with Beal and Moloch, one of the names under which the sun was worshipped. In fact the name signifies Sun Deity or Sun-God’ (Cooke 1875, 8-9). Sir William Petty (May 1623 – December 1687) in his survey, marks the church with the words ‘Umbilicus Hiberniae’.The stone was taken from Birr in 1828 by Thomas Steele to his residence Cullaun House, Co. Clare to honour Daniel O’Connell and used as a Mass Rock at that site. However, Cooke gives the date as 1833. It was returned to Birr Urban Council in June 1974 by the Dept. of Lands and placed in its present position.