In terms of scenery, the Tarmachan ridge is right out there with Scotland's other iconic ridges, such as the famous Aonach Eagach in Glencoe. But from a hill runner's perspective it also provides first class steady running along its entire length, save a short scramble on the western side of Meall Garbh. An outing of a good length can be had by taking in Beinn Ghlas, Ben Lawers, and Meall Corranaich, before ascending the Tarmachan along its northern ridge by the magical Lochan an Tairbh-uisge.
Tarmachan Ridge via Ben Lawers
For the initial ascent of Ben Lawers, see the route described here. From the summit, retrace your steps back to the bealach between Ben Lawers
and Beinn Ghlas, and take the path that contours the N corrie of Beinn Ghlas to the bealach below Meall Corranaich (NN 621 408). From the bealach a walkers path (not on the map) heads up Meall Corranaich. From the summit take the well defined path descending the SW ridge (again, not on the map). Near the end of the initial steeper descend the path splits -- take the right fork which curves onto the NW ridge line clearly visible on map, following a line of old fence posts along the nature reserve boundary. This path is damp under foot, and eventually, as the ground eases off around the 700m contour line, the peat hags take over in all their glory. Cut down onto the road by a line of your choice.
The ascent of Meall Tarmachan is via its N ridge, the dramatic cliffs of which run parallel to Lochan na Lairige. A high, double electric fence, with limited opportunities to cross, runs along this ridge for much of its length, starting from the head of the loch. You can either cross via a gate at NN 595 412, or, if you hit the road nearer the cairn marked on the OS map, little bit further via a stile at the point where the fence and wall start turning in westerly direction. Follow the fence (a faint path).
Beyond the summit of Creag an Lochain (842m), the electric fence deviates from the nature reserve boundary, heading nearly directly S, passing E of Lochan an Tairbh-uisge, while the ridge line curves SW. Care with navigation should be taken, particularly if visibility is poor. The corrie around the lochan is eerie and rather magical; its outflow provides a good water source, if required (there will be no more water until beyond the ridge).
Continue along the fence from the 842m summit, crossing it at a nearby stile, and shortly after that start turning SW. The reserve boundary follows a line of old rusty fence posts leading below a somewhat intimidating rockface at the start of the next ascent; this is turned on the right (N), then follow the natural ridge line, ignoring any sheep tracks higher up. The ground is grassy and quite steep at places.
From the summit of Meall nan Tarmachan follow the walkers path along the ridge. There is a short scramble on the descent of Meall Garbh -- care should be taken, especially if the rock is wet. Eventually the path descends the ridge down a corrie N of the 685m summit marked on OS map, picking up the water works access track around NN 568 367. A pleasant jog back to the start.
26km / 2000m ascent; allow 5-6 hours