Sydney Harbour Bridge Climb

AS far as I can tell it can only be done under the supervision of a professional company. There is fast traffic flowing on the bridge, if you were to even drop a tiny little thing from up top it could cause a potential road hazard. That is why they ensure that you have nothing loose on you -- even your spectacles are tied down to your body.

Not a particularly dangerous or skillful adventure, but spectacular fun nevertheless. Not for you if you are cant deal with heights.