The only wooden viaduct remaining on the British railway network, the Aultnaslanach Viaduct (also Allt na Slanach or Allt na Slanaich) is located on the Perth-Inverness railway in Strathdearn, a half-mile (1 km) west southwest of Moy Hall and 8 miles (13 km) southeast of Inverness. The viaduct crosses the Allt na Slanaich, a modest tributary of the Moy Burn.

Completed in 1897, this timber-trestle viaduct was the work of Murdoch Paterson (1826-98), Chief Engineer to the Highland Railway. It comprises five spans each of 7m (23 feet) and wood was chosen to minimise the weight of the structure, which crosses boggy ground. Given its unique nature, the viaduct was Category A-listed in 1976.

A £2.6 million restoration programme by Arup Scotland was undertaken in 2002 after rot was discovered in some of the timbers. A concrete structure was inserted to take the load of the railway, thus protecting the original viaduct.