Crossing the head of Loch Fleet, Thomas Telford's Mound is still serving the purpose for which it was built nearly 200 years later. It replaced an ancient Ferry at Littleferry across the narrow mouth of the loch, and while this actually added to the distance, it significantly improved the reliability of the northward route.
The Mound is an embankment, or causeway across the head of the tidal Loch. It is a wide structure (wide enough for a decent two lane single carriageway road and laybys), constructed with large blocks of stone filled with smaller stone and soil in much the same way as such structures are still built today. The dimensions are 7m / 23feet high; 55m / 60yards wide at the base and almost a kilometre / just over 1000 yards in length.
For nearly 60 years from 1902, The Mound was also the route of the Dornoch Branchline of the Highland Railway, which had a level crossing with the A9 at the southern end of The Mound.
At the northern end of The Mound, the A9 ramps up to cross the modern bridge across the River Fleet and the Railway line. This bridge is a large Concrete structure, bearing a strong resemblance to that at Helmsdale further north, and so presumably also dating from the early 1970s.
The original bridge designed by Telford still crosses the River Fleet, and is accessed from the small car park at the northern end of The Mound. The bridge opened in 1816, along with the rest of The Mound, although it was the first piece to be completed. Telford later extended the original 4 arches to 6 and modified the sluice gates in 1833. The gates regulate the flow of water out of the river, and prevent the tide heading upstream. They were also used to regulate the pressure of the tide whilst construction was still under way. Today the sluices are also used to control the movement of Salmon in and out of the river.