One thing's for sure — it's a mainstream adrenalin rush climbing the world's largest steel arch bridge in Sydney.

After signing an indemnity form, I slipped into a specially designed 'bridge boiler suit' and then got the once over from a staff instructor. Was this guy ex-military, I wondered? Anything that could fall during the climb had to be left behind, so I said goodbye to my wristwatch, wallet, keys and worst of all, my camera. Climbers are not allowed to take their own pictures on the bridge — a major bummer.

I was told to tie my sunglasses to my head, and a woolen cap, rain-suit and warm fleece lined jacket was wrapped up in the compartments on my suit, along with a holstered radio receiver and earpiece — used to communicate with the guide. There was a hint of cloak and dagger to all of this.

After double-checking that every loose part of my group's equipment was secure, the instructor took us through a brief training session of how to climb, where to step and how to hold on! We were connected to the bridge by an umbilical, waist high, steel cable for the entire trip and using the buddy system, relied on the climber behind for support in the event of anything going wrong.

BridgeClimb founder Paul Cave became hooked on the Sydney Harbour Bridge after he first helped to organise a youth group world congress bridge climb in 1989. He says from that moment on he wanted to share the bridge summit experience with as many people as possible.

It took Cave nine years to overcome the mountain of conditions and restrictions local authorities placed on his dream project and on October 1 1998 BridgeClimb was born. Today it's the top of every adventure visitor to Sydney's 'must do' list.

Survival training over, it was time to get out and conquer the 528 000 ton metal monster.

We were handed over to our hyperactive climbing guide Anthony, one of over 150 guides employed at BridgeClimb who told me he was drummer in Sydney's top rock band. He was born to perform.

"Let's go mates, higher, higher, no slacking allowed," Anthony's voiced chirped through the earphones. He was one of those irritating people who are always so cheerful you want to give them a good klap to make the world miserable again.

I trudged on, brave-faced, passed the first victory of crossing the catwalk, and then on to a vertical climb to the top of the eastern arch pylon, followed by the trek to the top of the main arch.

Things fall apart?

If ever the saying 'don't look down' meant something, now was the time. It had also started to rain hard, and my irritation at Anthony's cheerfulness was replaced by admiration for the way he somehow kept us all calm as the heavens opened up.

Slipping on the wet metal ribbon was a distinct possibility. I had no intention of testing the tensile strength of the umbilical cable. It was white-knuckle time. In between the rain and our careful steps Anthony gave us a stream of facts and figures about the bridge to keep our minds otherwise occupied. The one statistic that stayed with me was the six-million rivets used to secure this metallic monster. At least things weren't going to fall apart, I thought thankfully.

We reached the top, the rain stopped and as if on cue the brightest rainbow I have ever seen flashed across the harbour. There was only complete silence and burning calves. It didn't feel like the end of a 500-meter climb from base. The silence was broken by two climbers behind me sucking in air and shouting, "We did it, we bloody did it!"

That released the adrenalin and congratulations came thick and fast.

"Look down — you're on top of the Sydney harbour bridge mates," said Anthony, busy snapping pictures of us in brave Mount Everest summit type poses.

Back to earth on shaky legs

I glanced about at others in the group and they all had that satisfied group-spirit look people get when strangers are forced to bond quickly and then go on to achieve something worth writing home about. We were 134 meters above sea level with nothing more than a steel platform between our feet and the water. I could hear my heartbeat.

It's an unforgettable experience sitting on top of the bridge, with a 360° view that takes in Sydney harbour, with the famous Opera house, the city skyline, and the suburbs out to the horizon.

"Let's get on down mates," Anthony yelled. I was lost in my own thoughts as we headed back to mother Earth arriving on shaky legs.

The pictures were processed in a flash and we said our goodbyes, clutching photographic proof of the 'ascent' and watched as Anthony turned to greet the next group of nervous looking climbers.

"It's a tough climb, but you can't beat the view," I said to a particularly tense looking couple, and strutted off with a sense of new found energy. Getting high in Sydney had taken on a whole new meaning.

For more info visit www.bridgeclimb.com.