Ballochmyle viaduct

A southbound coal train crosses Ballochmyle viaduct (on the far side, making it hard to see). The structure was recently designated as a "national historic civil engineering landmark". The viaduct (located on the Glasgow & South Western line between Mauchline and Auchinleck) incorporates the largest single-span masonry arch in the UK, with a span of 181ft (55m) and height of 177ft (54m).
The viaduct cannot be reached by, or seen from the road, which may contribute to its relative obscurity when compared to other major viaducts in the UK. The only way to see it is from the river Ayr walk, a footpath alongside the river Ayr, which the viaduct crosses.