The Clarence Tunnel is a railway tunnel that was originally part of the Main Western railway line

Main Western railway line, New South Wales

The Main Western Railway is a major railway in New South Wales, Australia. It runs through the Blue Mountains, Central West, North West Slopes and the Far West regions.- Description of route :...

 across the Blue Mountains, New South Wales

New South Wales

New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...

, Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

. It is approximately 494 metres (1,620.7 ft) long.

History and description

The tunnel -- located to the west of Clarence

Clarence, New South Wales

Clarence is a place in New South Wales, Australia. It was originally a railway outpost on the original railway line across the Blue Mountains, but by 1908 when Clarence was used as headquarters for the Ten Tunnel deviation works, the town population had flourished to over 5,000 residents, the...

 -- was built by William Watkins and opened on 18 October 1869. The tunnel is almost entirely straight apart from a curve at the Clarence end and is the highest railway tunnel in Australia. The tunnel was closed on 16 October 1910, after being by-passed by a new deviation

Ten Tunnels Deviation 1910, New South Wales

The Ten Tunnels Deviation is the section of track between Newnes Junction and Zig Zag Box in the Blue Mountains, New South Wales. It was constructed between 1 June, 1908 and 16 October, 1910 to replace the Lithgow Zig Zag, which limited the length of goods trains over the Mountains.- Construction...

. After the tunnel's closure, it was utilised for growing mushrooms. In 1944, during World War II

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, the Royal Australian Air Force

Royal Australian Air Force

The Royal Australian Air Force is the air force branch of the Australian Defence Force. The RAAF was formed in March 1921. It continues the traditions of the Australian Flying Corps , which was formed on 22 October 1912. The RAAF has taken part in many of the 20th century's major conflicts...

 (RAAF) stockpiled chemical munitions

Chemical warfare

Chemical warfare involves using the toxic properties of chemical substances as weapons. This type of warfare is distinct from Nuclear warfare and Biological warfare, which together make up NBC, the military acronym for Nuclear, Biological, and Chemical...

 in the tunnel. The facility was known as No. 4 Sub Depot of No. 1 Central Reserve RAAF and was vacated by the RAAF in 1946. The tunnel was reopened in 1974 and forms part of the Lithgow Zig Zag

Lithgow Zig Zag

The Lithgow Zig Zag was a zig zag railway built near Lithgow on the Great Western Railway of New South Wales in Australia which operated between 1870 and 1910, to overcome an otherwise insurmountable climb up the western side of the Blue Mountains...

tourist railway.