Aug 1, 2014
Knapsack Viaduct, completed in 1867, was originally built as a rail bridge, and formed part of the zig-zag* railway at Lapstone, on the Sydney side of the Blue Mountains.
In 1926 this sandstone viaduct, designed by the railway engineer John Whitton, was widened to accommodate use as a road bridge. The viaduct remained part of the Great Western Highway until 1993, when it was replacing by a section of the M4 Western Motorway.
The viaduct, 57Km from Sydney, is now a pedestrian path/cycleway which continues down the hill to the end of the Great Western Highway at Emu Plains. Lucasville platform (left), can still be seen nearby.
When the first Glenbrook deviation was opened in 1892, the Lapstone ZigZag was abandoned, and John Lucas (Minister for Mines), lost the convenient rail link to his country retreat.
location map 'WildWalks' notes
* Sometimes known as the "Little Zig-Zag" to avoid confusion with the Zig-Zag railway on the western side of the Mountains