Another Ulster palace, quite as important as Emain Macha , was Ailech, the ruins of which are situated in County Donegal, on the summit of a hill 800 feet high, five miles north-west from Derry, commanding a magnificent view of Lough Foyle and Lough Swilly with the surrounding Country. It is a circular stone cashel of dry masonry, 77 feet in internal diameter, the wall about 13 feet thick at the base, and on the outside sloping gradually inwards. This central citadel was surrounded at wide intervals by five concentric ramparts, three of which may still be traded, the whole area originally including many acres. According to the old tradition it was founded by Dedannans [Tuatha de Dananns], and continued to be a royal residence to the time of its destruction, sometimes of the King of Ulster, and sometimes of the King of Ireland. After the fourth century it was the recognised residence of the northern Ui Neill kings, down to the year 1101, when it was destroyed by the Munster King Murkertagh, in retaliation for the destruction of Kincora by the Ulstermen thirteen years before. After this it was abandoned; and the kings of Ailech transferred their residence to Inis-Eanaigh - now called Inchenny - in the County Tyrone, near Strabane, where they probably resided till the arrival of the Anglo-Normans. For nearly eight centuries Ailech continued in a state of ruin, the wall being reduced to a height of about 6 feet; but during the years 1874-8, it was rebuilt - in the face of great difficulties - by Dr. Bernard of Derry, a man of culture, with antiquarian tastes, who, as far as he could, restored it to its original shape. The wall is now about 17 feet hight. It still retains - has all along retained - its ancient name, in the form of Greenan-Ely, where Ely correctly represents the sound of Ailigh, the genitive of Ailech.
Capital of Clan Owen
In early times the headquarters of the sub-kingdom of Owen had been at Aileach near Derry. For a number of centuries the kingship of North Western Ulster alternated more or less regularly between the two chief branches of the conquerors, the Clan Owen and the Clan Conall. As the Clan Conall found it more difficult to expand owing to its geographical situation, the balance of power shifted decisively to the growing Clan Owen. The series of victories won over Clan Conall by the Owen chieftain Hugh Allen and his kin resulted in the exclusion of Clan Conall from the over-kingship of the whole territory by the end of the eighth century. Thus Clan Owen became the dominant Northern dynasty, and their seat at Aileach became the headquarters of the over-kingdom now held by Clan Owen.
This honour for Aileach was not lasting. As power shifted farther south, deep into Tyrone, a new capital was required. Accordingly a more central position at Tullyhog, near Cookstown, was chosen. Professor James Hogan, in his work "The Irish Law of Kingship", places this transfer of the seat of kingship from Aileach to Tullyhog somewhere between the years A.D. 1035 and 1050. So in succeeding years Aileach became what it is today a relic of the past, massive in earth and stone, but haunted by insubstantial memories of departed glory. Alice Milligan's poem "The Dark Palace" catches its pathos:
"There beams no light from thy hall tonight
O house of Fame!
No mead-vat seethes and no smoke upwreathes
O'er the hearth's red flame;
No high bard sings for the joy of thy kings,
And no harpers play;
No hostage moans at thy dungeon rings.
As in Muircherteach's day."