Two Rock Mountain was marked on pre-nineteenth century maps as ‘Black Mountain’ though it has an older name, ‘Sliabh Lecga’, meaning ‘the Mountain of the Flagstones’. The current name and the old Irish name probably derive from the large granite rock outcrops known as tors, which protrude above the peat to the south-east of the summit. The tors were created by erosion and weathering along vertical and horizontal joints in the rock over many millennia. Other tors can be found on the neighbouring Three Rock Mountain. These remarkable geological features are the best examples of their kind in the Dublin and Wicklow Mountains. Two Rock is covered by wet and dry heath and blanket bog which provides a habitat for the endangered red grouse.

The summit of Two Rock is crowned with a large cairn that is believed to cover a Neolithic passage tomb, a type of burial monument. This cairn is known locally as ‘Fairy Castle’. The sub-circular, flat-topped cairn measures some 27 metres in diameter and 3 metres high. A possible passage or entrance to the tomb, referred to by locals as a cave, was visible in the 1940s but is no longer evident due to the collapse of the edges of the cairn. Passage tombs date from the Neolithic period, generally occurring between 3,500–2900 BC. They typically consist of a burial chamber accessed through a stone-lined passageway. The tomb was covered by a large cairn of stones with a ring of larger kerbstones used to define the perimeter.

Fairy Castle has never been excavated but it is believed to be the easternmost example of the complex of passage tombs that are found on the summits of the Dublin and Wicklow mountains. An important aspect of these mountain-top passage tombs is that they are intervisible. From Two Rock Mountain, the passage tombs to the west on Montpelier Hill, Tallaght Hill, Saggart Hill and Seahan Mountain can be seen. On top of the cairn is a trigonometrical pillar or trig point. This dates from the 1830s when Ireland was being mapped in detail for the first time by the Ordnance Survey.

When Red Hugh O’Donnell escaped from Dublin Castle in 1591, it is said that he crossed over Two Rock Mountain on his way to seek refuge with Felim O’Toole who had his stronghold at what is now Powerscourt in County Wicklow. O’Donnell was the son and heir of the chieftain of Tír Conaill (Donegal) and had been captured and imprisoned by the English three years previously. O’Donnell was recaptured not long after this escape but made a second successful attempt in January 1592. This time he succeeded in reaching Fiach McHugh O’Byrne in Glenmalure, although his fellow escapee Art O’Neill perished from exposure. O’Donnell’s escape is still regarded as a key event in Irish history. He returned to Donegal to become leader of the O’Donnell clan and forged an alliance with Hugh O’Neill in the Nine Year’s War. He left Ireland and died in Valladolid, Spain in 1602, reputedly assassinated with poison by an agent working for the English.

The Dublin Mountains Way traverses the summit of Two Rock, connecting the mountain with Tibradden and Piperstown to the west and Three Rock Mountain and Rathmichael to the east. The Wicklow Way passes along the western side of the mountain and extends from Rathfarnham in Dublin right through the heart of the Wicklow Mountains to Clonegal in County Carlow.

Text: Abarta Heritage

Link to Ticknock Recreation Site Features and Maps

National Monuments Service

NMS Historic Environment Viewer

DLR Libraries Local Studies Collection

Rathmichael Historical Society

[last updated 24.07.20]