Rathbeagh is one of irelands most historic monuments. The Rath is that of Heremon, son of Milesius. He erected his cheif residence and fortress at Rathbeagh on the river Nore. Heremon was married to Tea, an Egyptian queen, and after she died Heremon burried her under the mound of the hostages at Tara. Rathbeagh means the Rath of the birch trees. The Rath is of an oval shape, and very irregular. The diameters of it's greatest length and width being about 120 feet and 75 feet respectively. The interior is much above the level of the field, and is protected on one side by the river Nore, and on the other by a deep fasse or trench, ten or twenty feet wide. According to the four masters the milesian colony arrived in Ireland 1700 years before the birth of Christ. This date secures for Rathbeagh in connection with these primitive wonderers from the sunny land of Spain a very wonderful antiquity. Heremon after a reign of fifteen years died at Rathbeagh and was burried in the tumulus or sepulchral mound. Tuathe the legitimate built a residence on the Rath about 120 A.D. It is said locally that one of the kings living on the Rath coined his own money.
In 769 A.D. the Picts of Scotland making one of their raids into the south were defeated at the great bright fortress of weapons at Rathbeagh.
St Catherine's holy well, Tubber Naew Kathaleen, was a little to the south of the church, a few yards from the Nore but it has been destroyed.
O'Curry writes :-
"There was a well between the church [i.e., Rathbeagh church] and the Nore called St. Catherine's Well, at which a patron was held till within the last 10 years, on the 24th day of June ; and the 6th of December [i.e., Nov. 25th, old style] was kept a holy day in the parish in honour of St. Catherine."
"About half a mile north-west of the church of Rathbeagh, on the south side of the road is a heap of stones, with seven old white thorn trees growing round it; this the people call leact dubluing, i.e. Dubhluing's heap or monument, but they know nothing of it's origin."