Beinn Narnain suffers from being overshadowed, if that's the correct word, by its smaller neighbour Ben Arthur, better known as The Cobbler.
This is a shame, because Beinn Narnain is a fine mountain in its own right, and one that will definitely cause you to work for the views from the top as you tackle the rocky defences of the summit plateau itself.
The usual starting point is the large car park on the banks of Loch Long, just opposite Arrochar. The seaweed on the nearby high water mark should remind you that you will get no assistance from geography on this climb. It is literally a sea-level start, and you will see every single metre of the height of the mountain on your way up it.
Routefinding presents few problems in the early part of the climb. You simply cross the main A83 and follow the obvious path that makes its way up the forested hillside. The regular concrete blocks you encounter were once part of the foundations of a railway used in the construction of a nearby hydro-electric scheme.
As you reach the 330m contour, the well trodden path you have been following reaches a crossroads. Most walkers take a left turn here and follow the path that leads around the south of Beinn Narnain and onward to The Cobbler. You should take the much less frequented, less well defined, and in places pretty boggy path that leads directly onwards and upwards as you tackle the south east ridge of Beinn Narnain head-on.
Higher on the outlier of Cruach nam Miseag the underfoot conditions improve, and once past it there is a level stretch with even a hint of descent. It's only in poor visibility that you are likely to be lulled by this into any sort of false sense of security, because ahead of you lies the aptly named Spearhead. Don't worry, you'll recognise it when you see it, and it will certainly have your hands out of their pockets as you scramble up the gully to its right.
The summit plateau itself is adorned with a trig point and the views from it are superb in good visibility. East you can see Loch Lomond in the middle distance and the distinctive shape of Ben Lomond towering above it (just visible in the photo, top left). North is knobbly Ben Vane, and north west along the connecting ridge is Ben Ime, often climbed as part of a pair with Beinn Narnain.
Most striking, though, is the view south west down onto The Cobbler (bottom photo, right). Seen from here you get a much clearer sense of the layout of the mountain than you do from the normal view from Arrochar.
A nice circular walk can be had by descending Beinn Narnain generally west to the bealach with the Cobbler, then following the Allt a Bhalachaim south east to the Narnain boulders. From there take the well trodden tourist route back round the south side of Beinn Narnain to meet the route of ascent at the 330m junction: then back down to the car park.