Laigh Milton Viaduct

Laigh Milton Viaduct is a railway viaduct near Laigh Milton mill to the west of Gatehead in East Ayrshire, Scotland, about five miles west of Kilmarnock. It is probably the world's earliest surviving railway viaduct on a public railway, and the earliest known survivor of a type of multi-span railway structure subsequently adopted universally.The viaduct was restored in 1995–1996 and is a Category A listed structure since 1982. It bridges the River Irvine which forms the boundary between East Ayrshire and South Ayrshire.

It was built for the Kilmarnock and Troon Railway, opened in 1812; the line was a horse drawn plateway. The first viaduct was closed in 1846 when the railway line was realigned to ease the sharp curve for locomotive operation, and a wooden bridge was built a little to the south to carry the realigned route. This was in turn replaced by a third structure further south again, which carries trains at the present day.

Source: Wikipedia