The Picton railway tunnel (formally the Redbank Range Tunnel) south-west of Sydney was built between 1863 and 1867 as part of the original Main South line of the New South Wales Government Railways. Decommissioned in 1919 when the line was realigned, it was later used as a commercial mushroom farm from the 1950s to the 1990s (giving the tunnel its popular name). Since the mushroom farm's closure, the 181-metre tunnel has become one of the most-investigated paranormal sites in New South Wales, drawing attention from the Ghost Research Society of Australia and the Sydney-based paranormal community.
Three deaths are formally documented at the tunnel. The best-known is the 1916 death of 29-year-old Emily Bollard, a local woman who was struck by a steam train inside the tunnel and killed instantly; her body was discovered by railway gangers the following morning. Witnesses to her apparition — a woman in a long white dress with dark hair — have reported her presence inside the tunnel continuously since the 1920s. In 1926, a railway worker known only as 'Alfie' hanged himself inside the tunnel; reports of his shadowy figure and of the sensation of being choked have persisted. In the 1950s, a teenager died in a fall from the tunnel's ceiling ventilation shaft.
Organized paranormal investigations at Picton Mushroom Tunnel have produced some of the most-cited evidence in Australian ghost research. Ghost Tours Australia, operating nightly through the tunnel since 1999, documents an average of three to five unexplained temperature drops, unexplained voices, and physical-touch incidents per tour. Independent audio recordings have repeatedly captured female voices near the former '90-foot mark' where Emily Bollard was killed. In 2004, a formal infrared-camera survey conducted by the Paranormal Investigators Association reported a full-body apparition for 1.4 seconds in the tunnel's southern approach. The tunnel is now gated and accessed only via formal tours.