At 493m or 1617ft, Allermuir Hill is not the tallest hill in Pentlands: a dozen or more of the summits further down the range exceed 500m in height, and the tallest, Scald Law, reaches 579m. But as the tallest and most centrally positioned of the summits overlooking Edinburgh, Allermuir Hill is one of the most impressive and most often noticed hills in the range.
You can climb Allermuir Hill from a number of different starting points. A path from Hillend near Lothianburn leads up over neighbouring Caerketton Hill after climbing above the Midlothian Snowsports Centre, en route to Allermuir Hill. And Allermuir can also be climbed direct from Swanston or from Dreghorn on the Edinburgh side of the Pentlands.
The route described on this page assumes a starting point at the parking area close to the farmstead at Castlelaw. You reach it via a minor road that climbs for two thirds of a mile north west from its junction with the A702. The junction is signposted and is found about 2½ miles south of the Edinburgh City Bypass.
The path from Castlelaw Farmstead to the summit of Allermuir Hill climbs about 750ft over a distance of about 1.7 miles. The route follows a land rover track for most of its distance, before turning off for the grassy final pull up to the summit of the hill itself. Even after a wet period the route is largely dry, with a couple of short steep stretches towards the end.
You start by heading north from the car park through a gate and onto an obvious stony path. You should bear in mind that the path runs up the eastern edge of a military firing range. If red flags are flying to show this is active, make sure you don't stray into the danger area immediately to the west of the main path marked on the map displayed close to the car park (or on another near the summit of the hill).
Also just outside the military danger area is Castlelaw Hill Fort and Earth House, which lies immediately to the west of the path a couple of hundred yards from the car park. This is well worth exploring. The best view of the hill fort's ramparts is gained from a little further up the path, which then cuts round the east side of Castlelaw Hill, giving you your first glimpse of Allermuir Hill to the north. The best route up Castlelaw Hill itself cuts back south from the path you are following before you reach a high point at Fala Knowe, after which you descend briefly towards the saddle between Capelaw Hill and Allermuir Hill.
Before you reach the saddle, an obvious grassy path heads off to the right, following the west side of a stone wall up Allermuir Hill's cone-shaped upper reaches to a final turn in the fence. From here it is only a short and gentle final pull to the top. Here you find a trig point and a viewpoint indicator. According to the latter, on a clear day you can see Creuch Hill, 61 miles to the west; Ben Vorlich, 67 miles to the north west; Norman's Law, 34 miles to the north; and The Cheviot, 54 miles to the south east. The most obvious feature in the view needs no explanation: as you reach the top you find the whole of Edinburgh laid out at your feet.