This stone is now situated in the town of Birr, next to the Birr Heritage Centre or also known as Johns Hall.
The information board has this to say about it.
Referred to by Geraldus Cambrensis in the 12th Century as 'Umbilicus Hiberniae' ("The Navel of Ireland").
Probably part of a megalithic monument located at Seffin, the exact site of which now unknown.
Reputted by oral tradition to have marked a meeting place of the Fianna. 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.
Returned to Birr Urban Council in June 1974 by the Department of Lands. The stone is a block of limestone of lower carboniferous age around 250 million years old and is of local origin.