WHAT'S a birthday party without the guest of honour?

San Franciscans almost found out at last month's 75th anniversary of the Golden Gate Bridge, when the city's infamous fog threatened to roll in and obscure the birthday girl.

We flew into America's 13th largest city 75 years to the day that the audacious hunk of orange steel opened to the public. Everyone we met was holding their breath that the endemic mist would stay away for the elaborate celebrations because, as our cab driver explained, the bridge is often the first place that fog arrives and the last place it burns off. And, thanks to a particularly cruel meteorological quirk, the thickest fog usually appears in summer.

Fortunately, the good weather won out and the entire city was able to enjoy parades, music, dance, food, art installations and a fireworks display celebrating the second most recognised structure on the planet (after the Eiffel Tower). Somewhat ironically, the festivities took place everywhere but the bridge itself, a lesson learned after the 50 year anniversary when 300,000 people surged onto the span, creating human gridlock and 'flattening' out the bridge arch.

But what is it about the Golden Gate Bridge that attracts 10 million tourists a year?

It's no longer the longest suspension bridge in the world (that honour goes to Japan's Akashi Kaiko Bridge), or the tallest. It has never been the busiest. Yet there's something breathtaking about the art-deco structure that flings itself from San Francisco's shore to the green and wealthy headlands of Marin County: babies have been born on it, around 100,000 vehicles, 10,000 pedestrians and 6,000 cyclists cross it every day and its provided the backdrop to movies as diverse as Hitchcock's Vertigo, Monsters vs Aliens and the Weta-assisted Rise of the Planet of the Apes.

The city is overcoming its collective hangover the day we attempt to unravel the bridge's allure with a guided tour. Perhaps because officials have always viewed the bridge as a means of transportation rather than a tourist attraction, the first-ever guided tours started only last month.

Eight of us join our guide Grace for the 2.74 kilometre stroll across the Bridge to hear stories about how and why the vermillion structure came to be. We learn about the naysayers who said a bridge across the Golden Gate Strait, where San Francisco Bay meets the Pacific Ocean, couldn't be built, that it required an impossible feat of engineering to span the two miles of fierce tides and currents, strong winds and the ubiquitous fog.

Yet in the 1920s, engineer Joseph Strauss relentlessly championed the idea of the impossible bridge and eventually got his way. It took four and a bit years and US$35 million to build (around NZ$1.9 billion in today's money) but it was during the Great Depression when there was, apparently, no shortage of unemployed men willing to take on the dangerous work for the princely sums of $4 a day for labourers and $10 for skilled tradesmen.

If the Navy had had its way, the bridge would have been yellow with black stripes; if the Air Force had won out, it would have been red with white stripes; while others called for a black bridge (to hide the dirt) or a galvanised steel structure to create a streamlined look. Thankfully, architect Irving Morrow had the last say and opted for the distinctive hue, called "International Orange", which ensures maximum visibility in fog.

THERE'S a reason the old girl doesn't look her age. A 24/7 programme of maintenance means some section of the bridge is almost always being painted, repaired or replaced. It also supports its own police force, a fire truck with 1700 litres of water on permanent standby and four resident tow trucks.
One thing they won't mention on the tour, but will politely answer if you ask, is the thorny issue of suicide.

The bridge is arguably the world's most popular suicide platform, with an average of around 30 jumpers a year.

Grace tells me the first person leapt off a mere three months after the bridge was opened and the media stopped counting in 1995 in an attempt to deter jumpers. It obviously hasn't worked and as part of the 75th anniversary events, a group called the Bridge Rail Foundation, which works to prevent bridge suicides, staged a poignant display of 1558 pairs of shoes  some donated by victims' families  to represent the estimated number of people who've ended their lives on the bridge.

On the 75th anniversary itself, the San Francisco Chronicle reported another apparent suicide, when the body of a 40-year-old man washed up on the beach. In a macabre coincidence, 75 metres is the approximate height of the deck and 75 miles per hour is the approximate impact speed of suicide jumpers.

Grace explains officers who patrol the walkways bordering the span, on the lookout for potential jumpers, estimate an 80 per cent success rate in talking people down. At issue is the low railing (barriers would obstruct the view) but there is talk of erecting a suicide barrier, most probably an unobtrusive net. Apparently the design for a hanging steel net is currently being developed but, as always, someone needs to cough up the US$45 million for its construction.

We wind our way back to the brand new Golden Gate Pavilion, painted the same colour as the bridge, which features a steel model bridge tower built as a 'test tower' at Princeton University in 1933, along with photos, interactive displays and artefacts that tell the bridge's story.

Because of the fog, many of those who come to worship at the altar of the burnt-sienna structure each year never get to see it, so officials have installed a photo booth at the art deco Round House, which opened as a restaurant in 1938 but has since served as offices and a gift centre. Green screen technology means visitors can don hard hats and hi-vis vests and be photographed 'climbing' the bridge's main cable, no matter how foggy it is outside.

And if you weren't lucky enough to catch the 75th anniversary weekend, don't worry; the party continues throughout the year. There are treasure hunts, art and photographic exhibitions, installations, hiking events and even a symphony being developed in the grand old lady's honour. There's still time to celebrate what they called "a necklace of surprising beauty" on the day it opened 75 years ago.

FAST FACTS:

The Golden Gate Bridge Towers rise 227.38m above the water

There are abut 600,000 rivets in each of the bridge's two towers

If all 128,748km of wire used in the bridge's two main cables were connected end-to-end in a single strand, it would circle the Earth three times at the Equator

The Golden Gate National Park stretches 64km north and 64km south of the Golden Gate Bridge
High winds have closed the bridge only three times in its 75 year history: 1951, 1982 and 1983.

The bridge currently weighs 887,000 tons; it lost 12,300 tons in the 1980s when the roadway deck was replaced.

- © Fairfax NZ News