Encompassing the Mourne Mountains, the Mourne AONB was designated in 1986. It has a relatively "young" geological development and has a rich diversity of natural, cultural and built heritage.

Mourne Mountains

Famed in song and close to the heart of everyone in the Province are the Mourne mountains and their hinterland. Designated in 1986, it is one of the most picturesque mountain districts in Ireland. The twelve peaks include Slieve Donard, which at 850m is Northern Ireland's highest mountain. Beneath the cluster of fine peaks, cliffs and rock pinnacles, the mountain slopes descend through moorland, woodland, field and farm before meeting the coast. Slieve Croob lies as a northern outlier to the main massif

Further information on the AONB can be obtained from the Mourne Heritage Trust website.

Geology of Mourne AONB

Where did the Mournes come from?

The Mournes are comparatively 'young' mountains and are composed of hard, acidic granite. They developed when a vast block of ancient shale subsided deep into the earth's crust. As it did so, molton granite welled up in stages around the sides of the descending block and filled the 'roof cavity' left in its place. Their formation complete, the granite Mournes were still concealed beneath an overlying mantle of the original shale which has almost all since gone; worn away by millions of years of rain, ice and running water.

Since their formation some 50 million years ago, periodic climate changes have altered the mountains' appearance, notably the erosion and deposition which occurred during a series of Ice Ages. Ten thousand years ago the last ice sheets retreated, depositing in their wake vast quantities of sand and gravel. This covered the coastal plain to a depth of many feet, and included countless granite boulders swept down from the mountains. At higher levels the shape of many valleys were modified by the erosive power of advancing ice. The striking U-shaped profile of the Hare's Gap is one well know example of a pass shaped by the passage of ice.

Natural Heritage of Mourne AONB


Above 200m poor soils, low temperatures, high rainfall and a short growing season combine to produce a harsh climate for plant growth. These conditions also mark the limit of cultivation in the hills. Moorland soils tend to be shallow and poor in nutrients and support only those plants which can cope with such difficult conditions. Heathers and grasses grow well and carpet the hillsides and peaty ground throughout the Mournes. A range of other more unusual plants can be found at different elevations or close to bog pools. Several birds, animals and insects also have particular needs which only moorland or inaccessible parts of the Mournes provide. Birds such as peregrines and red grouse, which require luxuriant heather for food and shelter, are best looked for through the heart of the hills.


Improbable as it may seem, much of the moorland habitat on the lower mountain slopes has arisen through man's removal of trees and the prevention of regeneration by grazing livestock and occasional burning. The native woods that remain are few and far between. For example only one pocket of extensive oak forest survives, now protected as a nature reserve on the slopes behind Rostrevor. Elsewhere, planted woods enhance the landscape at Mourne Park, Tollymore, Castlewellan and Donard Park, where older stands of mixed broadleaved trees grow alongside more recent coniferous plantations. Stone walls rather than hedgerows are the common field boundary between the mountains and the sea, whereas inland of the mountains there is a distinctive mix of tall hedgerows, streamside woods, ribbons of trees and lakes trapped by drumlins.


The Mournes' coastal scenery has been shaped by the interaction of the sea with the land, by fluctuating sea levels and by erosion and deposition. Terraces which follow the shoreline near Glasdrumman and elsewhere mark 'raised beaches'. These indicate the position of the coastline during the last Ice Age, now left high and dry since the land rose following the retreat of the ice sheets. Sand and shingle drifted by currents has created the spectacular dune coast at Murlough and the sandy beaches at Cranfield. Along less accessible stretches (such as the headlands, terraces and eroding cliffs extending south from Newcastle) unimproved pastures, scrub and colourful communities for maritime plants fringe the shore, which in places also displays many features of geological interest. In contrast, the fjord-like inlet of Carlingford contains island outcrops, tidal mudflats and areas of saltmarsh important for a range of birds and other wildlife.

Cultural Heritage of Mourne AONB

Since the last Ice Age, man has altered the land around the Mournes to make a home for himself. Early Celtic settlers began the process of clearing land for agriculture while their roving herds of cattle and goats were the first domestic livestock to roam the hills. In former centuries, before today's farmland patterns were established, wealth was reckoned in terms of cows. Families moved with their animals to the mountain pastures from May to September. Only in the nineteenth century did sheep replace cattle in the hills.

At around the same time, an expanding population living on the land and the clearance of rough grazing for arable crops and potatoes led to the collapse of seasonal mountain grazing (called booleying). By the eighteenth century the use of granite as a building stone and its suitability, when cut and fashioned, for use as millstones, lintels, window-sills and door-steps gave rise to great local skills in splitting and 'dressing' stone.

Late in the nineteenth century better means of transport and an improvement in the type of cutting wedges used - consisting of a small iron wedge or 'plug' - made possible an export trade in dressed stone. Paving-setts, kerbstones, foundation blocks and stone monuments left the Mournes for use in new road and dock constructions in Belfast and Liverpool and Mourne granite is claimed to have 'paved Lancashire'.

Field and Farm

The farmland landscape of the Mournes is a result of centuries old agricultural practices. The earliest farmers began the laborious process of clearing the land of its Ice Age legacy of countless granite boulders. With the use of seaweed as field manure and lime to reduce soil acidity, the area under cultivation spread throughout the lowlands and pushed slowly up hillsides. Gradually the landscape which we associate with Mourne farmland became established, of which nothing is more evocative than the network of drystone walls - called ditches - which criss-cross the coastal plain. The skills which built them are still very much alive today.

Built Heritage of Mourne AONB

Prehistoric man in the Mournes was either very strong or an excellent engineer! The skill and organisation it would take to raise the granite capstone of Kilfeaghan Dolman (estimated weight 35 tons) would challenge even modern technology. Even more incredible is the tripod dolmen at Legananny where the flat granite capstone is raised high on three tall pointed stones. The beauty of these ancient tombs has made them a favourite subject for photographers and artists. 5000 years ago, when the dolmens were built, they were accompanied by a cairn of small stones, but often the cairn and even some of the giant stones disappear in time leaving only the heaviest stones.

Sites to visit

Slidderyford Dolmen

This is a good example of a tripod dolmen with large capstone and supporting uprights. It is opposite the entrance to Murlough sand dunes.

Dunnaman (Massfort) Court Grave

Court graves were used like family vaults for multiple burials. Dunnaman has an unusually long burial gallery, marked out with split granite side stones and divided into four sections. It is approached by a footpath north from the A2 beside the parochial house at Massfort.

Kilfeaghan Dolmen

This is a granite portal dolmen with a gigantic capstone and the remains of a long cairn. Signposted north of the A2 just west of the Causeway Water and along a path across two fields.

Kilbroney Standing Stone

In the field south of Kilbroney graveyard, 1 mile north of Rostrevor on the B25. There are many standing stones in the Mournes, mostly single like this one, but some in groups.

Legananny Dolmen

On the south side of Slieve Croob with a panoramic view of the Mourne mountains. Tripod dolmen with capstone gracefully balanced on three tall supporting stones.


The Anglo-Norman invasion of 1177 and continued challenges by the Magennises encouraged the building and maintenance of castles in this area from the late 12th up to the 17th century. Anglo-Norman castles were established at Clough and Dundrum in the late 12th and 13th century. In the 16th century a second wave of castle building began with tower-houses at Narrow Water, Castlewellan, Newcastle, Newry and Rathfriland. Only Narrow Water survives of this group, so we cannot visit a true Magennis castle, though they did capture and held castles at Dundrum and Narrow Water.

Clough Castle

An excellent example of an Anglo-Norman earthwork castle of the late 12th or early 13th century. The taller mound, the motte, was built of earth to provide a look-out position and the central defence. When excavated its top was found to have a wooden palisade, a stone hall across the centre and a stone tower half the size of the present one. The lower platform, the bailey provided a space for other domestic buildings and livestock. In the 15th century the look-out tower was enlarged to the size of a tower-house. When you climb the motte you realise what an important position the castle is in, overlooking the routes east to Downpatrick, south to Dundrum and north to Belfast Lough. The views from the top of the motte west to Slieve Croob are particularly fine.

Dundrum castle

A key castle in the Anglo-Norman conquest of Ulster in the late 12th century, on the site of a pre-Norman stronghold. Most beautiful of the northern castles, standing high above the town and Dundrum Bay, it features a tall circular keep at its centre, an inner bailey protected by a rock-cut ditch and an outer bailey with the ruins of the 17th century Blundell house.


This is a royal castle, built in the mid 13th century as part of the coastal chain guaranteeing a safe passage between Dublin and the north. A small mound nearby to the west may be the remains of an earlier castle and the ruins of a medieval church also survive. The views from the massive rectangular keep to the Mournes and across Carlingford Lough to Carlingford are spectacular. 4 miles south west of Kilkeel by minor roads from the A2.

Narrow Water Castle

Picturesquely sited on a promontory in the Newry river estuary, this tower-house was built for an English garrison in the 1560s. The tower has been re-roofed, with new floors and it stands within a bawn wall, an excellent example of its type.

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