City Underground

City Circle
View across Circular Quay, the halfway point of the city circle line.
Overview
Termini	Central
Stations	6
Services	T2 Airport, Inner West & South Line T3 Bankstown Line
Line number
Operation
Opened	20 January 1956 (1956-01-20)
Owner	RailCorp
Operator(s)	Sydney Trains
Technical
Line length	6 km (3.7 mi)
Track gauge	1,435 mm (4 ft 8 1⁄2 in) standard gauge
Sydney Trains services North Shore, Northern & Western Airport, Inner West & South Bankstown Eastern Suburbs & Illawarra Cumberland Carlingford Olympic Park

The City Circle is a system of largely underground passenger railway lines located in the Sydney central business district, in New South Wales, Australia, that make up part of the Sydney passenger railway 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.

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 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.