The original railway viaduct across Knapsack Gully was abandoned in 1913 when the line was re-routed to improve the grade and alignment of the tracks. As part of this work a new brick viaduct was built across the gully and this is still used today. The viaduct has eight arches and features simple brick detailling and a moulded sandstone string. It represents a final modification of the line to ease the arduous ascent into the mountains.
