- Rail Trail
- On Road
- Potential Rail Trail
- Other Trail
- former Railway
- The impressive sandstone viaduct over Knapsack Gully. When construction began in 1863 the viaduct was the largest in Australia, being 118 m long and 36 m high, with five spans of 16 m and two of 6 m.
- Remnants of zig-zag formation and Lucasville Station. The Lapstone Zig-Zag was the first full zig-zag constructed on any main-line railway anywhere in the world. The structure was later repeated on the western side of the Blue Mountains at the arguably more famous zig-zag railway between Clarence and Lithgow.
- The sandstone viaduct
- A network of walks and mountain bike tracks in the area, including to lookouts and the historic Lennox Bridge on the Macquarie Pass.
- Blue Mountains World Heritage Area to the west
- Sydney Harbour and CBD around 60 km east
Last updated: 14 January 2022
The Knapsack Viaduct and Zig-Zag are in the Lower Blue Mountains suburb of Lapstone.
Knapsack Viaduct is signposted from the M4 Motorway/Great Western Highway at the Emu Plains exit. From the car park at the junction of the old highway and historic Mitchells Pass, a concrete footpath rises gently and follows the former railway and highway route to and over the viaduct. From here, dirt paths (suitable for walking only) descend below the stone arches or climb to Elizabeth lookout, upper Zig-Zag ‘roads’ and Lucasville station.
Alternatively, the Zig-Zag and other sites can be approached from the top, from the east end of Knapsack Street.
An 634 metre-long 1892 tunnel, which bypassed the Zig-Zag, is located mainly south of the Great Western Highway. The tunnel is not open at this stage but Blue Mountains City Council are working on reopening it for cyclists and pedestrians. The entrances to the tunnel can be reached by walking tracks. The eastern entrance can be reached via a tunnel beneath the M4 to Governors Drive and then a track (overgrown at times) from near a water tank. The western end can be reached from the top of Tunnel Gully on the northern side of the Great Western Highway. Once closed in 1913, the tunnel was at times used to house a mushroom farm and to store mustard gas.
Lapstone viaduct walk
The viaduct from the top of the zig zag. (2009)
Junction on the Lapstone Zig Zag
Start of the Zig Zag walk
Walking track sign, Lapstone
Glenbrook tunnel - east entrance 
Glenbrook tunnel - west portal 
Glenbrook tunnel - west portal 
We acknowledge the Dharug people, the traditional custodians of the land and waterways on which the rail trail is built.
Development and future of the rail trail
Much of the abandoned rail route can be reached via the rail trail.
Rail line history
This section of railway including the Knapsack Viaduct and the Lapstone Zig-Zag was completed in 1865 and opened for traffic in 1867. The Lapstone Zig-Zag and Lucasville station were officially closed in December 1892 after the first (1892) Glenbrook Tunnel Deviation was completed.
Around 1910 the lower section of the track, including the historic Knapsack Gully Viaduct, was converted into the Great Western Highway, the main road up Lapstone Hill until the M4 motorway replaced it in 1993. The M4 motorway still utilizes part of the lower section of the zig-zag, which now un-available as part of this small rail trail. The first tunnel was also bypassed by a double track tunnel with a gentler grade at this time.