Passage graves usually cluster in two or more cairns, consisting of mainly a passage leading to a central chamber, corbelled roofed chamber sometimes in the form of a cruciform shape.
The perimeter of the cairn would be edged by kerbstones, like those of Newgrange, Co. Meath and Carrowmore, Co. Sligo.
Passage tombs are usually found in prominent locations, such as hill-tops.
Generally speaking, the less complex the passage tomb is the older it is considered to be.
The possible passage tombs atop Cairn hill are considered to be among the oldest in Ireland along with Carrowmore, Co. Sligo.

The hill is particularly important for the two possible passage grave structures atop it.
The largest example is Cairn A (or Carn Caille), marking the highest physical point of the hill with a diameter of 18 m and height of 3 m. Reference to that cairn does not appear until 1960, when Ordnance Survey Ireland installed a trigonometrical station, partially damaging the cairn.
An excavation took place before installation, with cremated bone recovered from a central rectangular chamber.
Thanks to the advent of Global Positioning System technology, the trigonometrical station is now redundant.
 The second cairn, Cairn B, is about 50 m to the north of Cairn A, with a 9 m diameter and difficult to identify due to the extensive coverage of peat and heather.
Passage graves usually cluster in two or more cairns, consisting of mainly a passage leading to a central chamber, corbelled roofed chamber sometimes in the form of a cruciform shape. The perimeter of the cairn would be edged by kerbstones, like those of Newgrange, Co. Meath and Carrowmore, Co. Sligo. Passage tombs are usually found in prominent locations, such as hill-tops. Generally speaking, the less complex the passage tomb is the older it is considered to be. The possible passage tombs atop Cairn hill are considered to be among the oldest in Ireland along with Carrowmore, Co. Sligo.
The hill is particularly important for the two possible passage grave structures atop it. The largest example is Cairn A (or Carn Caille), marking the highest physical point of the hill with a diameter of 18 m and height of 3 m. Reference to that cairn does not appear until 1960, when Ordnance Survey Ireland installed a trigonometrical station, partially damaging the cairn. An excavation took place before installation, with cremated bone recovered from a central rectangular chamber. Thanks to the advent of Global Positioning System technology, the trigonometrical station is now redundant.  The second cairn, Cairn B, is about 50 m to the north of Cairn A, with a 9 m diameter and difficult to identify due to the extensive coverage of peat and heather.
Carn Clonhugh