The Kyle of Tongue is a tidal sea loch on the north coast of Scotland, narrow enough that a bridge is plausible and exposed enough that building one is not trivial. The 1971 solution was elegant: a 3.8-kilometre causeway from the eastern shore that lands on Tongue Island - Eilean Thunga in Scottish Gaelic, a natural island near the mid-point of the kyle - and then continues over a concrete bridge to the western shore. The bridge itself has eighteen spans supported by twin piers, totalling 183 metres of carriageway. It carries the A838, the trunk route between Thurso and Durness, and was fully refurbished in 2011 to extend its service life. The structure is functional rather than ornamental: pale concrete, low-slung, and built to survive sea-loch tides and the kind of Atlantic gales that the Sutherland coast routinely produces.

Before 1956 there was a passenger ferry across the kyle, a small open-boat service that linked the road on the eastern shore to the village of Tongue on the western side. It saved walkers and travellers the long detour around the loch's head, but it was weather-dependent, did not run at night, and could not carry vehicles. When the ferry stopped, the only crossing for anything larger than a sheep was the ten-mile loop south through Coldbackie and Borgie. For fifteen years that was the only option. The bridge, when it finally opened in 1971, was less a marvel of modern engineering than a long-overdue convenience - the kind of project the north coast of Scotland tends to wait decades for, then quietly accepts as essential within a season.

The bridge sits in one of the most theatrical landscapes in mainland Britain. To the south rise Ben Loyal at 764 metres and Ben Hope at 927 metres, both Munros, both dominant features of the Sutherland skyline. The village of Tongue sits on the western shore with the ruin of Castle Varrich on the rock above it. The kyle itself, when the tide is in, mirrors the mountains; when the tide is out, the sandflats stretch like a pale sheet from bank to bank. Walkers stop on the causeway to photograph the view. Cyclists on the North Coast 500 route - the 516-mile loop of the northern Highlands that has transformed tourism in the area - cross it as one of the route's landmarks. For drivers, it is simply the section where the road finally relaxes after the climbs and twists of the inland route - one long, straight line across the water before the next climb begins.