Overview
Ben Crom (Irish: Binn Chrom, the “stooped” or “curved” peak) is a 526-metre granite summit in the heart of the Mourne Mountains, County Down. It’s nowhere near the height of Slieve Donard, and most people who come here never go up it at all – the real draw is the reservoir it stands over and the quiet valley walk in to reach it. A good track runs the valley floor to the dam, with steeper ground branching off for anyone set on the top.
One thing worth knowing before you plan: you can no longer drive up to the dam, and there’s no shuttle. Everything here starts on foot from the Silent Valley car park.
The granite landscape
Ben Crom’s character is all geology. It sits in the central Mournes, in the G3 phase of the Mourne granite. On the south-western flank there’s a clear contact line where the older, grey, closely jointed G2 granite meets the lighter, finer G3; the summit crags are cut by dark porphyry dikes, magma that forced through the cooling rock long after. Glaciers did the rest, gouging steep scree on the eastern and north faces and leaving the western slopes smoother. Climbers know the crags too – the routes here run mostly in the HVS to E2 grades. For everyone else the payoff is the contrast between the sharp eastern rock and the gentler western approaches, and the long views over the water to Slievelamagan.
The dam and water supply
After the Second World War, Belfast needed more water storage, and the Water Commissioners chose the upper Silent Valley over the originally planned Annalong site. Building started in 1953 – the contractor was Charles Brand and Son Ltd, and a workforce of 186 finished the job in 1957.
Unlike the earth dam down at Silent Valley, Ben Crom is a mass-gravity concrete dam, holding itself up by sheer weight. It runs about 700 feet (210 m) along the crest and holds roughly 1.7 billion litres, its core packed with concrete and granite “plumbs” of up to five tonnes each. In 2012 Northern Ireland Water spent £1.6 million refurbishing it. Together with the Silent Valley reservoir below, it supplies much of Belfast and County Down; the two hold close to 21 billion litres between them.
Walking to the dam
The main outing is simply the walk in. From the Silent Valley car park a granite-lined road – built with stone from the Annalong tunnel – runs up the valley to Ben Crom dam, open to walkers and cyclists. It’s roughly three miles (about 5 km) each way, mostly gentle and well-surfaced, so a there-and-back is a comfortable half-day rather than a quick stroll; the full waymarked Ben Crom Dam Walk comes in around 10.5 km and takes 3.5 to 4.5 hours. There’s a shorter Heritage Trail of about 3 km (an hour) near the car park for anyone with less time.
For the summit itself, a steady climb leaves the valley through heather and rock and tops out in two to three hours, with rocky, sure-footed ground near the top. The Shelter Stone – a slab of granite jutting from the hillside to form a low roof – is one of the Mournes’ best-known wild-camping spots and a handy rest stop if you’re heading up.
Practical information
- Parking and charges: the Silent Valley car park holds about 120 cars, first come first served, and it’s not free – £5 a car, £1.60 per pedestrian, with rates for coaches and mini-buses too. Come early on summer weekends.
- Opening hours: Silent Valley Mountain Park runs seasonal hours – roughly 9am to 6.30pm in spring and autumn, until 9pm in high summer, and until 4pm through winter. It also closes outright at times, most recently for storm damage, so check the NI Water site before you drive out.
- Facilities: there are toilets at the Silent Valley car park; the nearest shop and café are in Annalong.
- Dogs: welcome, but keep them on a lead near the water, the intake structures and grazing sheep.
- Access: the valley road is smooth enough for the opening kilometre, but this is a long walk to the dam and a rough climb to the summit – neither suits wheelchairs or buggies beyond that.
- Care: the whole area is within the Mourne Area of Outstanding Natural Beauty and a protected water catchment, so stay on the tracks and take litter home.
Weather and safety
The Mournes catch a lot of rain, especially late summer and autumn. Check the Met Office forecast before you set out; after heavy rain the dam’s spillways run hard and the reservoir-road surface turns slick. Winter walking is fine with the right footwear and layers, but the granite underfoot and the exposed tops ice up. Mobile signal drops in the upper valley, so carry a map or offline GPS.
Since you can’t drive in and the park keeps seasonal hours, the single thing to check before leaving home is the NI Water page – for the day’s opening time and any storm closure. Then it’s a straightforward walk to one of the range’s most striking reservoirs.