The townland of Rathbeagh is named for an ancient double ringed fort on the River Nore in the parish of Lisdowney near Ballyragget, County Kilkenny. According to Irish tradition, the Rath is the burial place of Heremon, son of the Celtic Taoiseach Milesius, noted in the Book of Leinster as 1560 BC. The Gaelic name is Rath Beithigh, meaning "the Rath of the Birch trees." It is located in an ancient valley once called Mágh Airgid Rois ("The Plain of the Silver Wood"). Both names possible point to Silver Birch trees.
It consists of a flat-topped oval mound about 41 metres (135 ft) north to south and 36 metres (118 ft) east to west. A fosse 3.7 metres (12 ft) wide surrounds the mound, leaving a gap at the river's edge. Outside there is a rampart about 3 metres (9.8 ft) high. The whole structure overlooks a bend on the Nore. The river is fordable at this location, so strategically the fort controlled the crossing. Parts of the Rath are being eroded by the presence of livestock in the field.
The remains of a church dedicated to St. Catherine is located in the graveyard situated just about 300 metres (980 ft) north of the Rath. The church is built on the site of an earlier castle or stronghouse. Remains of what are believed to be stables or workshops were discovered in the adjacent field. The earliest gravestone date that can be distinguished in the graveyard is 1715. This church is one of a handful of fortified churches peculiar to this area in north Kilkenny. Other examples can be found in Threecastles and Freshford.
Just East of the old church is a pond under the road, known locally as Poll Leabhair, meaning "the Pond of the Book" or "Hole of the Book." According to tradition, the church was desecrated during the Cromwellian wars, and the Missal was dumped in this pond. In the mid-19th century the church bell was found in a sand-pit in a nearby field and was presented to the Church of Ireland Church in Killeshan, Carlow, according to Carrigan's History of Ossory.
A well nearby is known as St. Catherine's Well. Its specific location is unclear, but it is somewhere a short distance south of Poll Leabhair and between the field known as The Paddock and the river Nore. Oral history records that the well's water was very popular as a cure for eye disease.