The Ten Tunnels Deviation is a heritage-listed 9.2-kilometre (5.7 mi) section of the Main Western Line between Newnes Junction and Zig Zag stations in Lithgow, New South Wales, Australia.

[2] When they opened in 1910, the tunnels replaced the Lithgow Zig Zag, which limited the length of trains over the mountains and required two changes in direction.

[2][4][5] The original 1869 Main Western single line headed north from Mount Victoria along the ridge known as the Darling Causeway.

[2] The Ten Tunnel Deviation started at Newnes Junction and finished at Bottom Points (now Zig Zag platform).

[2] Supplies to the line during construction were provided by a funicular railway that descended 107 metres (350 ft) from the ridge to a location near No.

Originally eleven were planned, but one of them was opened out instead, owing to the discovery of rock faults, leaving the deepest cutting on the New South Wales rail system.

[3] The supply of materials for tunnels 8, 9 and 10 was expedited by the construction of a 110-metre (350 ft) funicular[2] of the 4-rail type from near Mount Sinai on the original line.

[9] The deviation comprises ten tunnels of varying length from 70 to 825 metres (77 to 902 yd) that carry the double-track 1,435 mm (4 ft 8+1⁄2 in) standard gauge Main Western line between Newnes Junction and Lithgow Zig Zag stations.

[2] As at 28 April 2010, the Ten Tunnel Deviation is of state significance due to its historical associations with the second phase of railway crossing across the Great Dividing Range.

It is of a high level of technical significance as a large scale engineering achievement of the early 20th century including excavation of the deepest cutting on the NSW rail system.

The project was one of the great railway deviations constructed throughout NSW, and was a success in reducing both journey time and track gradient, and continues to be in use today.

[2] Ten Tunnels Deviation was listed on the New South Wales State Heritage Register on 2 April 1999 having satisfied the following criteria.

The Ten Tunnel Deviation is historically significant as the second phase of the Great Dividing Range railway crossing.

[2] The place is important in demonstrating aesthetic characteristics and/or a high degree of creative or technical achievement in New South Wales.

[2] The place has potential to yield information that will contribute to an understanding of the cultural or natural history of New South Wales.

[2] The place possesses uncommon, rare or endangered aspects of the cultural or natural history of New South Wales.

[2] This Wikipedia article contains material from Great Zig Zag Railway deviation tunnels, entry number 01037 in the New South Wales State Heritage Register published by the State of New South Wales (Department of Planning and Environment) 2018 under CC-BY 4.0 licence, accessed on 2 June 2018.