You can see this rock outcrop very clearly while on the Portlaoise bypass (M7). The best way up to it is to turn off for the Heath (commons) and then pretty much follow the direction of the castle all the way. There is a car-park below the rock. Really amazing place you can feel the history.
Dun Masc' or the fort of Masc, as it was known by the Celts, is one of the most historic sites in Ireland. It's ruins date back thousands of years. Dunamase was even known to Ptolemy, who called it Dunnum and named it in his famous map of the world in The 2nd Century. The Rock stands 150 feet tall in the heart of what is otherwise a flat plain, and was ideal as a defensive position with its veiw right up to the Slieve Bloom Mountains. Pre-Celtic Bronze age settlers were the first to fortify it, followed by the Celts themselves. Among them was King Laois Mor, who gave his name to the country. The Vikings Plundered it in 845, and in the 13th century was given to Strongbow the Norman as a gift from his new son-in-law, Diarmiud Mac Murrough. It is Mac Murroughs castle which lies in ruin atop the rock today. The Castle went through some major changes of ownership over the years after this. Through Bargaining and back-stabbing (most likely in a very literal sence) it passed through the hands of Strongbow to the Anglo-Norman Mortimer family, and from them to the decendents of Laois Ceann Moore. The O'Moores, who used it as a staging point from which to make the Normans lives a living hadies.The O'Moores renovated the Mac Murroughs castle quite extensively in the 15th century, and they sucessfully defended it for over a century until the arival of the planters, who displaced the O'Moores and exiled them to Kerry along with the Fitspatricks, the O'Dempseys and the O'Dunnes in 1607. Finnaly, Oliver "the butcher" Cromwell saked the castle in 1650. One can still see the trenches where his troops were based. A Beloved Family pet still roams the ruins of the Rock. An unearthly, fire-breathing Black hound by the name of Bandog. Legend says he guards treasure buried deep inside Dunamase.
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