It's the City of Sydney's vision of George Street transformed: a tree-lined boulevard accessible only to pedestrians and trams from Bridge to Liverpool streets.

But the extent to which the car-choked artery could be remade as "one of the world's great plazas" has already been rejected as wishful thinking by the state government, which is adamant the pedestrian zone detailed in a new council exhibition is not what it will build.

Just how much of George Street should be shut off to cars is the subject of ongoing lobbying by council as the state plans its $1.6 billion light rail project.

The Council, which is contributing $220 million to its city component, on Thursday opened an exhibition called Next Stop: 21st Century George Street, which depicts the CBD street being closed off to traffic for 400 metres beyond the area announced by the government last year.