Common Mountain is isolated from most other hills by its location in the apex of a narrow fork of land, where the N56 meets the R230. It used to be regarded as an Arderin, however measurement on 13 Nov 2019 reveals that it's height is 499.7 and so just under the requirement.

For the easiest ascent, it is hard to ignore the lay-by parking at G687 859 A, which is already at an elevation of 270m. From here you need to outflank the forested area, either by heading northwest along the road for 100m, or southeast about 100m to the hairpin bend, before heading south over open ground. Once around the forest you can head east towards the summit. An hour should see you at the summit and an up and down should take well under two hours.

An alternative is to start right in the hook of the hairpin bend, where you'll see some small hills of gravel. Behind these is a gate. This has a 'Private Property' sign, but judging by the towering weeds on either side, it hasn't been opened in years. Across the gate is a short track leading down to a stream. Cross this and you are onto to the open hillside, which is grassy and firm underfoot. Head directly east for an hour to reach the top.

Common Mountain can be linked with a climb of Crocknapeast. From Common, descend to a broad col at G698 848 B (sh 384) before heading south to Crocknapeast. On the descent, you are probably best returning via the same col; a circuit of three hours.

From the summit, very steep ground to the north and east points towards a possible circuit from that direction.

There are a number of 'No Trespassing' signs scattered around the hill. Linkback: https://mountainviews.ie/summit/453/comment/5212/

According to the OS this summit has a summit height of 501m, however checking with a survey quality GPS on 13th Nov 2019 revealed that the true height is 499.7m +/- .1m

We climbed a mountain and came down a hill. Linkback: https://mountainviews.ie/summit/453/comment/20681/

I started this walk from the scenic viewpoint and carpark (687859 A) at the head of the Glengesh Pass, a fantastic drive up through a steep sided valley along hairpin bends to gain height. At the hairpin bend just below the carpark there is a gate and rough track heading onto the hillside. This is accompanied by a sign saying 'private no entry', joining a plethora of other such signs up through the valley. I politely ignored the sign, dropping down, crossing a stream and started climbing the open hillside. The views along the valley soon open out to include the magnificent coastline of the area, including Slievetooey. Cross an easy area of peat hags and pick up the remains of an old wall heading uphill. A broad top is reached in 30 mins, with views stretching across Donegal Bay to the clear line of the Sligo Hills and the Ox mtns stretching westwards. A further 15 mins NE brings the summit of eroded peat and some stone, with a small cairn and 'OS pillar', or concrete filled plastic pipe as it is more commonly known as in these parts. A much more satisfying route is visible from here, taking in the natural horeshoe of steep slopes to the N & E. The views from the summit take in the remainder of Donegals hills - the Bluestacks and the Derryveaghs. To the S I could see the boats in the fishing port of Killybegs.
I returned SW and trhen S along the broad top on good ground, picking up a fenceline. Where the fence turns to avoid an outcrop of rock, cross and head down towards the col at point 384m (698848 B). The ground looks terrible from here but is not too bad to cross. Pick up a newly constructed fence and follow as it turns and heads uphill, but veer off S for the top of Crocknapeast (497m), reached 45 mins after Common. Pass some pools of water at the top and then drop and rise as follow around the rim of the valley containing the Crow river. A line of old rotting fence posts show the way, with great views to the top of Crownard to the S. Reach the top of Mulnanaff (475m) and contour around another river valley dropping down from this line of hills. Head downhill now towards a stand of conifers and pick up a waymarked way (663826 C). This is very wet and could better be characterised as a streaam in many places. A stream is crossed, with the help of a guide rope (666837 D), and a lane provides easier passage. This joins the road heading back to Glengesh and 45 mins of walking does the job. A walk over a good part of the Glengesh hills, good views, no other people, not the best weather, enjoyable day. Linkback: https://mountainviews.ie/summit/453/comment/2560/

Started from the lay-by near the top of the Glengesh Pass. Walked south past the forestry before squelching SE across boggy moorland. A messy but easy ascent to the skyline brings you to a fence which can be followed for a distance. Gradient steepens slightly before you arrive at the summit, marked with a concrete-filled plastic pipe atop a peaty knoll.
Good views include down to Ardara and Loughros More Bay, and northwest to Meenacurrin / Slievetooey. Linkback: https://mountainviews.ie/summit/453/comment/1931/

Summit of Common Mountain with Ardara and Loughros More Bay in the distance Linkback: https://mountainviews.ie/summit/453/comment/1932/

I took this snap of Common Mountain after I drove through the Glengesh Pass having climbed Sliabh League earlier in the day. Incidentally on the cover of the Discovery Series Map 10 is a picture of the Glengesh Pass and the mountain to the right of the road is Common Mountain. Linkback: https://mountainviews.ie/summit/453/comment/1809/