A crane has toppled over the roof of one of Sydney's newest and tallest buildings, Barangaroo tower.
It's believed the four-tonne spider crane was lowering a cherry picker when it collapsed, leaving it dangling precariously over the side of the building.
Hundreds of people have been evacuated but no one has been injured on the ground, and an exclusion zone is now in place.
Traffic has been significantly delayed on the road below, which has also been closed to pedestrians.
Work is now underway to get the crane down from its precarious 51-storey perch.