As someone who is not very fit AND scared of heights, I was worried when I was given a Bridge Cimb as a gift. I needn't have worried. Attached with a safety rope throughout, and most of the time climbing gentle steps (just like normal stairs), I felt perfectly safe. There were a couple of hairy moments when we had to climb short ladders (I could see the ocean beneath my feet), but there was really no danger.
The view is good, but not as high as many of the skyscrapers in Sydney, or Sydney Tower, so don't expect it to be spectacular. The difference is seeing the view, perched in the open air instead of safely behind plate glass.
The preparations take much longer than the climb itself, so that is a consideration if you are short of time in Sydney.
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