Castleknock Castle Castleknock Castle is a ruined Norman castle located on the grounds of present - day Castleknock College , Castleknock , Dublin , Republic of Ireland . Description . " " The position of the castle is commanding , and its two deep ditches , and the ruins of its massive walls , bespeak its former strength . The Castle itself is thickly clad with ivy , and the entire hill covered with large and spreading trees . The whole is now reserved ground , enclosed with a strong fence . The solemn gloom of the place , its dark winding walks , and the profound silence that reigns around , make it a delightful solitude . " " A mound may have preceded the present medieval Norman structure . The polygonal keep was the notable feature of the castle . Attached to it was a large squat building . A curtain wall , interspersed with towers , surrounded the castle . There is a moat or ditch constructed around the castle . Today , the site is surrounded by trees while the ruins are seldom visible from the road except in winter . The earliest extant drawing of the castle by Francis Place also shows it in ruins , but somewhat less dilapidated than at present . There is also a small mound to the west of Castleknock College buildings known as Windmill Hill . There is a water tower there now which was built originally as an observatory by a previous owner , Simon Guinn . History . Cromlech . There is evidence of the site ' s importance prior to the erection of the castle in the Norman period . An ancient pagan cromlech was discovered . " " In the year 1861 , an ancient Cromlech , or Druid ' s altar , was discovered in the interior of the old Castle when digging the grave of the Rev . Thomas Plunket . The workmen , coming on a large flat stone , found it too heavy to remove , and immediately commenced to break it . They succeeded after great difficulty , but on detaching a portion , they found , to their surprise , an empty space beneath , and a human skeleton lying at full length . The head and larger bones were almost perfect , and with them were small heaps of dry , whitish dust . The men not understanding the nature of their discovery , placed the bones a little aside , and continued their work . It was not till the grave was filled up , and it was too late to remedy the evil , that the whole matter came to light . From the description given by different persons who were present , there is no doubt that the discovered grave was one of those ancient Cromlechs , or altar tombs , which were used as burial places for kings or notables during the Pagan times . The skeleton in this case was so old that the admission of air caused a portion of the bones to fall into dust ; this accounts for the small heaps of whitish dust which were found with the larger bones . " " Cnucha . " " In the year 726 " , say the Four Masters , " died Congalach of Cnucha . " In the old translation of the annals of Clonmacnoisc , he is called " Konolagh of Castleknock . " In the Annals of Ulster we read " Congalach Cnucho moritur ; and in the Annals of Tigernach " Congalach Cnuchaensis moritur . " We know nothing respecting Congalach , but that he died at his fort , Cnucha , towards the beginning of the eighth century . " " Castle origins : the Baron of Castleknock . The castle was founded by the Norman knight , Hugh Tyrrel , who was later created Baron of Castleknock . He chose this location near the end of the esker which stretches from Galway to Dublin . Built on two mounds of the esker , it commanded the route into Dublin from the west . Castleknock was the final rallying point for the forces of the last High King of Ireland , Rory O ' Connor . He failed to drive the Cambro - Normans from the area around Dublin in 1171 . " At that time the old fort underwent many changes . Tyrrel strengthened his fortress with all the improvements of modern warfare , and in a short time the Norman castle stood aloft in grim defiance , with its heavy battlements and deep double ditch . The battering ram could not approach it , and the missiles thrown against it fell harmless to the ground ' as hailstones from the rounded shield . ' " " . " Foundation of Abbey by Richard Tyrrell . The Abbey of St . Brigid was founded where the Protestant church now stands , by Richard Tyrrell , second Baron of Castleknock , in 1184 , and continued to flourish until the suppression of the monasteries , when it was demolished , and a Protestant church built on the site . In ancient times Castleknock furnished two canons to the Cathedral of St . Patrick , and still today two prebends of St . Patrick ' s derive their titles from " Castrum Noc ex parte diaconi , et Ca - strum Noc ex parte praecentoris " . Capture by Robert the Bruce . The Bruces advanced on Dublin ( 1316 ) . A short time before , Edward Bruce had been crowned King of Ireland at Dundalk , and thinking the time had come for the expulsion of the English , he invited his brother Robert to his assistance . The King of Scotland landed in Ireland with a select body of troops , and , being joined by his brother , marched to besiege Dublin with 20 , 000 men . The first exploit on approaching the city was the taking of Castleknock . It could not be expected that the old fortress , long deemed impregnable , could long hold out against the hero of Bannockburn . Bruce entered , making Hugh Tyrrell prisoner , and fixed there his headquarters . It was now believed that the liberation of Ireland was at hand . There was feasting and rejoicing in the Castle . The Irish and Scottish chieftains met at the same board , and plaids and bonnets mingled , with garments of saffron hue . But joy quickly gave place to gloom . Bruce soon perceived that Dublin was fully prepared for a siege , and well provided with provisions from the sea . Moreover , the ardour of the citizens caused him to relinquish all hope . After remaining a few days in the Castle , he released Tyrrell on payment of a ransom , and retired from the city . But he had scarcely commenced his march , when he seemed to repent of his resolution , and halted again at Leixlip . After a short delay he recommenced his march towards the south , and soon after left Ireland , leaving his brother to continue the war . Legend . " THE LADY OF THE CASTLE ; CTR THE STORY OF EIBHLEEN O ' BRINN . " Of all the facts connected with the history of Castleknock , there is none that has attracted more interest at least , amongst a certain class than the story of Eibhleen O ' Brinn . Dr . Burton , in his History of the Royal Hospital , Kil - mainham , has developed it into a tale of considerable length , and an anonymous writer in the Nation has commemorated the event in not ungraceful verse . The facts are as follows : In the early part of the 16th century , Hugh Tyrrell , the last of the name , ruled in Castleknock . During his absence , his brother Roger , by his violence and licentiousness , made the old castle the terror of the neighbourhood , and a " stronghold of iniquity . " One summer ' s evening , Roger carried off Eibhleen , the fair daughter of O ' Brinn , or O ' Byrne , a Wicklow chieftain , who dwelt on a hill to the west of the neighbouring town of Chapelizod , and confined her in the turret of the castle . At dead of night , the maiden heard steps ascending the stone staircase that led to her apartment , and fearing the worst , opened a vein in her neck , by means of her breast - pin , and bled to death . Next morning the fact was divulged , and great indignation was expressed against Tyrrell . Turlogh O ' Brinn had taken refuge in the pale from the horrors of war , and hoped to bring up his family in peace , under the protection of the viceroy . The affliction which now befel this peaceful chieftain , excited universal sympathy . At this time , the site of the Royal Hospital , Kilmainham , was occupied by the Knights of St . John , and one of them , who , as procurator of the house , had become acquainted with the family of O ' Brinn , resolved that so public a scandal should not pass unpunished . He consequently assembled his retainers , and marched towards Castleknock . Tyrrell , finding he was to be attacked , declared that he would not take refuge behind his ramparts , but would meet his enemy in the open field . A bloody battle ensued , in which Tyrrell was slain . His tragical end was considered a just punish - ment for his many crimes ; but the death of the maiden was long regretted by the people , and often in the winter ' s even - ings , when the rustics gathered round the blazing hearth , many a tear was shed over the sorrows of O ' Brinn , and the fate of his daughter Eibhleen . It was long a popular belief , that , at the hour of midnight , a female figure , robed in white , might be seen moving slowly round the castle . This , they said , was Eibhleen , and they called her " The Lady of the Castle . " " When distant chimes sound midnight hour , The spirit pure is seen ; And moving round the lonely tower , Looks bright as moonlight beam . And as the moonbeams tint the walls , And light the turret ' s crest , " ' Twas hence " , she says , " my spirit fled , ' Tis here my bones find rest . And here I wander , year by year , For such my lot has been , But soon at end my penance drear , I ' ll rest in joy unseen . ' " Her act of suicide , though wholly unjustifiable , was believed to have been palliated by ignorance , and in making the rounds of the castle , she was supposed to be completing her purgatory . The Lady of the Castle has not been seen since the Congregation of St . Vincent got possession of Castleknock ; the priests , they say , must have " laid the spirit . " Impact of the English Civil War . " COURAGEOUS CONDUCT OF AN IRISH LADY AT THE TAKING OF CASTLEKNOCK " Castleknock Castle was the scene of many bloody encounters , including this one recounted by an Irish officer in 1642 . It was discovered in the Bibliothèque Imperiale , Paris . A small pamphlet entitled " Courageuse Resolution d ' une dame Irlandaise a la prise de Chateau - knock " , was lately found by accident in the Bibliothèque Imperiale of Paris . It occupies only six pages I2mo . , and seems to have been a letter written by an Irish officer to some friends in France , very soon after the event took place . It was found at the time so interesting that it was immediately published and circulated through Paris . No name is given , but its date is 1642 . It is entered in the Bibliothèque Imperiale , 8vo . No . 955 , A . a . It thus commences : " The Earl of Ormond , a Protestant , went forth from the city of Dublin on the 28th of last month at the head of 4 , 000 - foot and 500 horse towards the county Meath . " The next day he besieged with his army Castleknock , belonging to the Lady de Lacy , aunt of the Earl of Fingal . The husband of this lady was engaged in the army of the Catholics of Ireland . He left his wife in the Castle to keep it with fifty men only , being well assured that her courage was above her sex , in which he was not deceived ; for this lady , by the orders which she gave , caused 400 soldiers of the besiegers to be slain during the four days the siege lasted , and the number of dead would have been greater still , had not the ammunition failed , which this lady having perceived , she caused to be put in one heap all her clothes , money , jewels , and precious moveables , in a word , all that was found of any value within the enclosure of the Castle ; she then set fire thereto , so that there should remain no booty for the enemy . She also rendered useless all the arms which were in the place , having caused them to be broken , with the exception of those with which her soldiers were equipped , and in the light of the fire she harangued her soldiers thus : " My faithful servants , you can well judge by th action I am after performing , what hope there is of favour from our enemies , and how little clemency I expect at their hands . I tell you , moreover , that you should not expect quarter from them , but remember the sentence which says , ' let the vanquished hope for nothing from their enemies . ' Take courage , then , and combat to death for the faith of your Redeemer ; you can never find a more glorious end , and the sooner to find it , go valiantly to attack the enemy of the Cross , lest , being made prisoners , any of you should , by bad treatment or the violence of torments , fail in the good resolution you have taken of dying to - day for the Catholic Faith ; in which I desire to set you the example by marching at your head . ' " This done , the besieged set fire to the Castle , and went down , sword in hand , with such resolution that , after a great carnage of their enemies , all that went forth remained dead on the field , with the exception of the lady , who was made prisoner by the Earl of Ormond . " After this the Earl sent to Dublin for reinforcements , and pursued his march . " Thus terminates this interesting narrative . " " General Monk . The castle was partially dismantled after the War of the Three Kingdoms when considerable artillery damage had been done to the castle . " " When the English Parliament proclaimed war upon King Charles , the Irish adhered to the Stuarts , and the lords of Castleknock joining the national movement , planted the royal standard upon their battlements . From that day their doom was fixed . General Monk marched from Dublin with a strong force and siege train , and sat down before the castle ( 1642 ) . Things were there in the same state as in the days of the first Tyrrells . The lofty walls , the deep - set windows , the rooms within low and dimly lighted , and the heavy oak benches around , more like machines . of war than articles of luxury . But the garrison was too weak for the defence . A heavy cannonade commenced , and when the walls were shaken to their foundations , and eighty of the defenders had fallen , the signal was given and the place taken by assault . The garrison had acted bravely , but compassion was far from the hearts of the Republicans . The survivors were tried by cburt - martial , found guilty of fighting against the state , and hanged from those walls they had so bravely defended . Monk , on returning to Dublin , left a strong force in the Castle , for , though much shattered , it was still a position of considerable importance . But its days were numbered . " " Owen Roe O ' Neill . On his march towards Dublin ( 1647 ) , finding Castleknock in the hands of the English , he determined to dislodge them . An effort was made to avert the blow . Colonel Trevor appeared at the head of a body of cavalry , but these were quickly routed , and O ' Neill commenced another siege . This was too much for the veteran fortress , already tottering to its fall ; it surrendered , and breathed its last in the hands of the Irish hero . Present day . " The green plot of ground enclosed within the old walls is used as a burial place for the priests of St . Vincent de Paul , and many zealous missioners , cut off in the bloom of life , are there interred . It was a happy thought . That spot , purpled with the blood of many a hero , and containing within its bosom the relics of the " departed brave " , is now a consecrated cemetery . Here rest side by side the soldier and the priest of Erin . The one fought for Ireland ' s temporal interests , the other for her spiritual welfare . . "