Also known as Zig Zag Historical Railway, is located between Clarence and Lithgow. It is a historic railway line by which the Main Western Line could scale down the western escarpment of the Blue Mountains Range via a series of reversals or "Zig Zags". Opened in 1869, the Zig Zag was a major civil engineering feat for its day. Steam locomotives had to work hard to climb its steep grades. Over time, due to the dependence on rail traffic, this section was a liability and became an operational bottle neck. The Zig Zag was by passed in 1910 by a ten tunnel deviation.