The Khojak Tunnel (aka Sheilla Bagh Tunnel) is a 3.91 kilometres long railway tunnel located in Killa Abdullah district of Balochistan near Pak-Afghan border at Chamman, province of Pakistan It is located 1,945 meters above sea level.
The tunnel was constructed in 1891 under the Khojak Pass and remains one of the longest tunnels in South Asia, and the longest in Pakistan. It is expected to be surpassed by the 8.6 km Lowari Tunnel, currently under construction, in 2009.
It was featured on the old Rs. 5 banknote.
It was constructed in 3 years and it is so straight that they (still) use a mirror to reflect light at one end which is visible from the other. The legend says that the engineer building the tunnel committed suicide because both end of the tunnel did not meet on the day he calculated, later the reason was found that workers did not work one day and filled bogus logs.