The steel span, delivered under police escort in a complicated operation through CBD streets in the dead of night, was described as a major milestone by Lord Mayor Adrian Schrinner.

The $190 million Kangaroo Point bridge, currently under construction, will span 460 metres across the river and link the City Botanic Gardens with Scott St on the other side.

The council hopes the structure, due to open in 2024 sporting an 83-metre high mast and an over-water restaurant, will become a must-visit destination for residents and visitors as well as a major active transport link for the city.

The installation of the span, the first of eight, involved the transport of two 45-tonne steel modules down Edward St before they were lifted into place by a mobile crane.

Four more are due to be installed by the middle of this year as the bridge comes together pice by piece from both sides of the river.

Project contractors BESIX Watpac will also begin lay the concrete bridge decking in coming months.

The Kangaroo Point bridge is the most spectacular of the collection of green bridges planned or under construction. The smaller Breakfast Creek green bridge is likely to be the first to be completed.