City Circle

The City Circle is a mostly-underground railway line located in the Sydney central business district, in New South Wales, Australia, that forms the core of Sydney's passenger rail network. The lines are owned by RailCorp, a State government agency, and operated under Transport for NSW's Sydney Trains brand. Despite its name, the City Circle is of a horseshoe shape, with trains operating in a U-shaped pattern. The constituent stations of the Circle are (clockwise): Central, Town Hall, Wynyard, Circular Quay, St James, Museum and back to Central.

History and description
The original concept for the City Railway was part of a report dated 1915 submitted to the government by chief railway engineer, John Bradfield, upon his return from overseas study, with work commencing the following year. His concepts were largely based on the New York City Subway, which he observed during his time in New York City.

Built in stages, the first City Circle stations to open were the heritage-listed Museum and St James, which both opened in 1926 as part of the initial electrification of Sydney railways. Next was the "western limb" through Town Hall and Wynyard, which opened in 1932 in conjunction with the opening of the Sydney Harbour Bridge. This section contains four tunnels. Two connected to the Harbour Bridge, while the two City Circle tunnels terminated at Wynyard. In 1956 the dead ends at St. James and Wynyard were joined and the "missing link", Circular Quay – was opened. Central and Circular Quay stations are above-ground (Circular Quay is elevated, directly underneath the Cahill Expressway), while the remainder are underground. Several unused railway tunnels also exist. The former tram tunnels at Wynyard, and other stub tunnels at St James are well known.

Services and operations
The current service patterns generally consist of trains from the Bankstown & Inner West & Leppington lines operating around the City Circle in a clockwise manner via Town Hall station. This track is known as the "City Outer". Trains from the Airport & South Line generally operate around the City Circle in an anti-clockwise manner via Museum station (using the "City Inner" track). Bankstown line trains towards Liverpool only also operate around the City Circle in the anti-clockwise direction on weekdays. A set of flying junctions at Central enable this pattern to be varied.

Prior to the integration of the Eastern Suburbs line into the Illawarra Line in 1980, Illawarra line trains also operated around the City Circle.

Trains on the Western and Northern lines usually do not proceed around the City Circle but instead, proceed across the Harbour Bridge to the North Shore line and vice versa.

Stations
The line has six stations.