Knapsack Viaduct in the Blue Mountains

Welcome to Knapsack Viaduct, the majestic sandstone arch bridge tucked into the lush gullies of the Blue Mountains. Originally built in the 1860s as part of the historic Lapstone Zig Zag railway, this remarkable structure stands as both an engineering feat and scenic highlight. Steeped in history and easily accessible via a short bushwalk, it’s a must-visit for anyone exploring the region, especially on a Blue Mountains tour.

A Legacy of 19th Century Engineering

Design and Construction

The viaduct was designed by John Whitton, the celebrated Engineer‑in‑Chief of NSW Railways, and constructed by W. Watkins between 1863 and 1865. This sandstone marvel comprises seven arches—five spanning 50 feet and two of 20 feet—built at an incline of 1 in 30 to carry the original single-track line across Knapsack Gully.

When it opened in 1867, the structure was celebrated as the finest piece of masonry in New South Wales, extraordinary in scale and craftsmanship.

From Railway to Roadway

Used until 1892, after which the railway was rerouted via Glenbrook Gorge, the viaduct earned a second life in 1926 as part of the Great Western Highway. Its stone parapets were extended to support two car lanes and later widened in 1939 with a concrete deck to accommodate increasing traffic.

Ceasing highway use in 1993 when the M4 bypassed it, the viaduct was reopened in 1995 as a heritage-listed pedestrian and cycling link, preserving its structural grandeur and historical integrity.

Exploring the Lapstone Zig Zag Walk

Getting There & Trail Overview

Start your journey from the carpark at the end of Knapsack Street in Glenbrook or from Mitchells Pass. The well‑graded track follows the old railway alignment, stretching approximately 3 km return, and takes about 1.5 hours at a moderate pace.

Wheel-friendly up to Top Points Lookout, the track is also dog-friendly on leashes, making it perfect for families and casual walkers.

Highlights Along the Way

• Top Points Lookout: Offers a treed panorama over Knapsack Gully, though views are somewhat obscured.
• Knapsack Stairs: A descent of over 100 timber steps that takes you close to the viaduct’s arches—great for photos and radiating historic charm.
• Lucasville Station Ruins: Reveals remnants of the platform once used by local politician John Lucas in the 1870s.

The Gully Floor View

Descending further into the gully, you’ll feel dwarfed by the towering sandstone arches—about 40 m high and 118 m long—while fern and rainforest canopy create an enchanting, echoing chorus of birdsong.

Why It’s a Blue Mountains Staple

• Historic significance: A pivotal piece of infrastructure in the first railway ascent into the Blue Mountains—arguably the world’s first main‑line zig‑zag.
• Scenic beauty: Juxtaposition of dramatic stone engineering and verdant gully forest makes for striking imagery and exploration.
• Accessibility: Short, graded trails mean it caters to a broad range of visitors, offering both convenience and immersion into natural heritage.

Conclusion

Knapsack Viaduct stands as a testament to ingenuity, perseverance, and adaptation—from railway to highway to walking trail. If you’re planning a Blue Mountains small group tour, this iconic structure offers a captivating snapshot of NSW history, stunning natural surroundings, and easy access for all types of explorers. Their footsteps may have been the first on that zigzag path, but your visit will keep the legacy alive—step by step, arch by arch.