The Far North Line, like the A9 road north of Inverness, follows the line of the east-facing Moray Firth coast. In places the railway is almost on the shore, the track running along the raised beach produced as the land rose following the end of the last Ice Age. This route provides some spectacular coastal scenery. If possible sit on the right hand side of the train when leaving Inverness for the best views.
The road route north of Inverness enjoys three relatively new bridges: across the Moray Firth (between Inverness and the Black Isle), the Cromarty Firth and the Dornoch Firth. The railway takes a longer but more scenic route. It loops inland from Tain to Lairg, which has never been on the A9, a diversion intended at the time of construction to open the centre of Sutherland to trade since much of the population of the far north of Scotland is concentrated in coastal areas.
The route then returns to the coast at Golspie. Beyond Golspie, the railway continues along the coast as far as Helmsdale, then inland up the Strath Kildonan and across the Flow Country to Halkirk and back to the east coast at Wick. At Georgemas Junction near Halkirk, the line divides with a branch to Thurso.
More details of the rail route and the traffic on it is provided by the Friends of the Far North Line: http://www.fofnl.org.uk/
The ScotRail site provides a commentary about what to look out for when travelling the route: https://www.scotrail.co.uk/scotland-by-rail/great-scenic-rail-journeys/far-north-line-inverness-thurso-wick