Slieve Bloom Mountains – Arderin Peak

Overview

The Slieve Blooms are among the oldest mountains in Europe – geologists reckon they once stood over 3,700m high, and hundreds of millions of years of erosion have worn them down to the rolling 527m plateau you see today. That long history, more than any drama in the skyline, is the character of the place. The range straddles County Laois and County Offaly, rising from the central plain as blanket bog, heath and pockets of conifer and native woodland – a quiet refuge for walkers and wildlife.

The highest point, Arderin (527m / 1,729ft), is a broad bog-covered summit with views on a clear day to the Wicklow Mountains, the Dublin skyline and the Galtees. If you want one trailhead that rewards the drive, make it Glenbarrow for its waterfall and varied terrain. Come prepared for wet ground, though: this is soft, boggy walking, and the bog stays waterlogged long after rain.

History and legend

The Slieve Blooms formed around 400 to 450 million years ago, part of the same mountain-building that raised the Massif Central in France, which makes them among the oldest ranges in Europe. Erosion stripped away the towering peaks, leaving the weathered, rounded profile of today.

The range marked the northern boundary of the ancient kingdom of Osraige, and later Upper Ossory. Mythology runs through the hills: legend has Fionn Mac Cumhaill raised on these slopes by his aunts, Bodhmall and Liath Luachra, who taught him a warrior’s skills, and a cave linked to his boyhood is still pointed out locally. The name Sliabh Bladhma derives from Bladma, a mythic figure of the old tales. Ring forts, megalithic tombs and stone alignments scattered across the uplands show continuous human presence from the Neolithic on.

Walking and hiking

The Slieve Bloom Way is the backbone of the network: a 70km waymarked long-distance route, usually walked over three days or taken in shorter sections. Alongside it run 17 looped walks, colour-coded green (easy), blue (moderate) and red (challenging), from six trailheads – Glenbarrow, Clonaslee, Cadamstown, Kinnitty, Glenafelly Forest Car Park and Glen Monicknew.

Key routes and loops include:

• Glenbarrow Waterfall Loop (4.5km, strenuous) – A forest path climbing through mature plantation onto bogland and finishing at the Glenbarrow falls.
• Silver River Nature Trail (7km, strenuous) – Near Cadamstown, following a tributary through native bog and heath.
• Giant’s Grave Loop (11km, strenuous) – A longer circuit past a megalithic tomb tied to the Bladma legend, with extended ridge walking.
• Kinnitty Castle Loop (4.5km, moderate) – Quiet woodland paths with a visit to the castle grounds and village amenities.
• Arderin Summit – Reached by a short, direct bog path from Glendine Gap or a longer approach from Glenbarrow. The top is marked by a modest cairn and an Ordnance Survey pin.
• Extended ridge walks – Link Arderin with neighbouring summits such as Wolftrap Mountain (487m) and Baunreaghcong (509m) along the Slieve Bloom Way.

There are also 35km of mountain-biking trails, with blue and red routes from the Kinnitty and Baunreagh trailheads, and a mountain-biking festival held each year in late April.

Nature and wildlife

Much of the upland is the Slieve Bloom Mountains Nature Reserve, which at over 2,300 hectares is Ireland’s largest state-owned nature reserve – a Ramsar wetland and a Special Area of Conservation and Special Protection Area. The blanket-bog ecosystem is the defining feature: sphagnum moss, sundews and heather on the plateaus, with oak and birch in the sheltered valleys. It supports breeding hen harrier, red grouse, merlin, peregrine falcon, golden plover and curlew, and snow bunting arrive in winter. Spring and early summer bring heather in flower and the most bird activity; late autumn often clears the air for the longest views.

Getting there and transport

The mountains are best reached by car. The R422 (Rosenallis to Clonaslee) and the R440 (towards Kinnitty) lead to the main trailheads. The nearest service towns are Portlaoise (about 30km north) and Birr (about 25km south).

Public transport is limited for direct trail access. Bus Éireann routes serve Portlaoise and Birr, but reaching the car parks at Glendine Gap, Glenbarrow or Kinnitty needs a local taxi or your own vehicle.

Nearby attractions

After a day on the hills, several historic and cultural sites are within easy reach:

• Castle Durrow – An 18th-century estate with formal gardens and guided tours of the demesne.
• Aghaboe Abbey – Atmospheric ruins of a 6th-century monastic settlement in quiet woodland.
• Clonaslee – The main gateway village to the Slieve Bloom Way, with a heritage centre and craft shops.
• Emo Court – A neo-classical mansion and parkland designed by James Gandon.
• Birr Castle – Home to the historic Leviathan telescope and formal gardens, a short drive south in Offaly.
• Clonmacnoise – A UNESCO-listed monastic site on the Shannon, with seven churches, a round tower and royal tombs.

Practical information

Access points and parking

Trail options to Arderin

Visitor information

• Official website: slievebloom.ie
• Contact: Slieve Bloom Outdoors, +353 86 8210056, enquiries@slievebloom.ie
• Opening hours: Open year-round. Trail conditions vary seasonally; check the website for bog and path updates.
• Events: The Slieve Bloom Walking Festival runs over the May bank holiday weekend; the mountain-biking festival is in late April.
• Parking fees: Free across all main car parks.

Tips for visitors

• Weather shifts quickly in the midlands. Pack waterproofs, a warm mid-layer and boots with good grip.
• Boggy sections turn slippery when wet. Trekking poles noticeably improve stability on the approach to Arderin.
• Carry a physical map or a charged phone with offline mapping; the signal can be patchy on the plateau.
• Keep dogs on a lead in spring and early summer to protect nesting hen harriers and other ground-nesting birds.
• Aim for early morning or late autumn, when the air is clearest and the midland plains show best from the summit.