After Tara and Uisneach, Knock Aillinn is the most historic hill in Ireland--that is, if it was really the seat of the celebrated Finn, the son of Cumhail. It is a different hill from the hill of Allen, which is about nine miles north of it, and must not be confounded with it, although, as it will be shown further on, the confusion of the two hills seems to have taken place very long ago indeed. Knock Aillinn is some five or six miles south of Newbridge, in the County Kildare. Apart from its historic interest, it is well worth visiting, for it is situated in a rich and beautiful part of the country, and the view from its summit is one of the fairest and most extensive to be seen in any of the eastern counties. Eastward the view is obstructed by the Wicklow mountains, but on every other side it is very extensive, for Knock Aillinn is 600 feet high. So fine is the view from this hill that O'Donovan, the celebrated Gaelic scholar, was inspired by it to write a poem in Irish in praise of it, when he was employed on the Government Survey in 1837. The poem may be seen in his unpublished letters in the Royal Irish Academy. One verse of it, translated into English, will show that it is a composition of more than ordinary merit:-- "Beautiful the view from the hill of Aillinn, Over lofty hills and fair plains, Over mountains wreathed in veils of cloud;-- The view will remain in my memory for ever." But beautiful and extensive as the prospect is from Knock Aillinn, and greatly as the lovers of the beautiful may enjoy it, the chief interest possessed by this hill is historic rather than scenic. On its summit is to be seen the most gigantic of all Irish raths. O'Donovan called it "prodigious." The whole top of the hill is surrounded by a mighty rampart of earth, four hundred yards in diameter, that encloses over twenty acres. After nearly two thousand years those earthen ramparts are still of great height; and when, according to the fashion of the times, they were topped with a strong palisade of timber, Knock Aillinn might be said to be an almost impregnable fortress. To render it still stronger, the hill on which it is placed is steep, and its ascent difficult. It was on this hill that some think the renowned in Celtic song and legend, Finn, the son of Cumhail, had his stronghold; but others, and it must be confessed that they are the most numerous, think that Finn's dun was on the hill of Allen, some eight or nine miles to the north.