If you close your eyes and think "Sydney", the white-tiled sails of the Sydney Opera House are probably among the first images that spring to mind.
They have become iconic not just of the nation's most populous city but, for many, are also synonymous with Australia itself.
The World Heritage-listed building has been the site of tens of thousands of events in its near-50-year history — upwards of 38,000 have been staged in the last two decades alone.
With close to 11 million visitors to the Sydney Opera House each year, odds are you've also ventured inside its famous sails.
However, the general public has rarely been invited behind the scenes — until now.
A new, three-part ABC TV series, Inside The Sydney Opera House, takes a look at how productions are staged and the inner workings of the building, from the recently completed multimillion-dollar refurbishment to its hidden, underwater workshop.
As the site of many milestones and public controversies in the nation's history, the opera house is a treasure trove of stories, but the series lifts the curtain on some of its lesser-known facts.
Here are five things you may not know about the Sydney Opera House.
1. More than 1 million tiles are checked by hand
The sails of the opera house cover an area of around 1.62 hectares and are adorned by more than 1 million shimmering, white tiles: 1,056,006 to be precise.
Every five years, these tiles must be individually hand-checked by a team of six engineers and abseilers, led by building operations manager Dean Jakubowski.
"The Sydney Opera House has to be one of the most important buildings in the world. It deserves the care and the amount of maintenance we put into it," Jakubowski tells ABC Arts.
It takes around 30 minutes for Jakubowski's team to make the 22-storey ascent to the top to inspect the tiles.
"We basically go over the side, start at the top and make our way down and tap every single tile," he says.
"We have a model of the building and we record every single tile's condition so that, if any repairs are required, we can easily go back to that location."
Jakubowski's team performs a "tap test" on the tiles and listens for changes in pitch to determine their condition.
If a tile is "drummy" — that is, if its adhesive has worn down — the tap test will produce a dull but high-pitched sound.
"What you'll get is an air gap between the structure and the tile and you can actually hear that it makes a really very obviously different sound when you tap it."
The inspection process takes six weeks.
"There's no better way of doing an inspection than actually getting up there and looking at it visually, feeling it and hearing it yourself," Jakubowski says.
Not just a pretty face, the tiles are an important barrier against the elements.
Specialist heritage consultant and architect Alan Croker says they act as a sort of "raincoat" for the building, protecting it from water damage and salt build-up from the harbour.
The tiles are fired at a very high temperature, which makes them impervious (meaning: they have a water absorption rate of less than 0.5 per cent), but Croker says they still need to be checked meticulously.
"Over time, they can gradually detach and, if one of them was to slide off, that's like a roof tile sliding from a 10-storey building. It's a bit dangerous, not only for people but the damage it could do to the building itself," Croker says.
Croker has been integral to conservation efforts at the Sydney Opera House for the past 20 years. He inspects the building every two weeks to make sure the conservation standards set by Danish architect Jørn Utzon are being adhered to.
In developing the tiles, Utzon was inspired by Japanese ceramics and Iranian mosque tiles, Croker says.
"There are two variations: One is a very shiny, high gloss and the other one is flat, no gloss. It's exactly the same tile but one has an undulating, slick glaze on it, which is clear," he says.
"[Utzon] likened this to the effect of sunlight … between snow and ice."
Utzon commissioned Höganäs, a Swedish manufacturer, to create the bespoke 12-centimetre square tiles, now known as the Sydney Tile. Höganäs mimicked the subtle granular texture Utzon had seen in Japanese ceramic bowls by mixing a small amount of crushed stone into clay.
While these tiles are no longer produced, there are 48,000 spares kept in a Sydney warehouse for a rainy day.
2. The house is heated and cooled by seawater
In the bowels of the building lives an air-conditioning system that dates back to the 60s.
Seawater is drawn directly from Sydney Harbour and circulated through 35 kilometres of pipes, powering both the heating and cooling of the opera house.
"It goes through four, large heat exchangers and that's where it takes out the heat from our domestic water to be able to cool it down," Jakubowski says.
Bucking the traditional cooling tower model, the system was considered innovative for its time, Croker says.
"I think there [were] only one or two other buildings in Sydney that were using it.
"Even now, it's still considered state-of-the-art," he says.
The pipes are cleaned out once a week, often yielding barnacles and mussels — approximately 400 kilograms annually — which are then recycled, along with the rest of the opera house's food waste.
This system also requires regular maintenance to prevent corrosion from saltwater, Jakubowski explains.
"But the environmental impacts [are] much better than having a conventional cooling tower on top of your building," he says.
The air-conditioning system also plays an important role in meeting the staging requirements of the opera house.
Because temperature and humidity affect the tuning of instruments, when the Sydney Symphony Orchestra is playing, the temperature is set to 22.5 degrees Celsius.
"Each company, or each artist, has really particular specific needs. The opera require it to be slightly cooler on stage [21C] … [because], generally, they're wearing larger, heavier costumes," Jakubowski says.
"Whereas, a ballerina thrives in a warmer setting [23C] because … their flexibility is better.
"If you have a comedy show in the Concert Hall, they want the venue to be really, really cold. So, there are no two hirers that are the same."
3. It is home to the world's largest mechanical action organ
Boasting some 10,244 pipes and weighing 37.5 tonnes, the Concert Hall Grand Organ is the largest of its kind in the world.
Designed by Sydney-based organist Ronald Sharp in the late 60s, the organ took 10 years to complete. (It was finished in 1979, six years after the opera house's official opening.)
Positioned above the choir stalls at the southern end of the Concert Hall, the organ reaches 15 metres in height, is 13m in width and is 8m deep.
While the organ features in Utzon's original design for the interior, it was embellished by his successor, Peter Hall, after the function of the hall was changed. (Utzon famously resigned after a public stoush with the then-state Liberal government, at which point Hall stepped in.)
Croker says the organ in Utzon's design was intended to be more mobile.
"[The hall] was meant to be a multipurpose auditorium, not a dedicated concert hall. So [Utzon's] idea was that there would be an organ, which would move up into that position when it was required, [but] when a proscenium arch was required … the organ would be down below the stage," he says.
When the proscenium arch was removed from the design, Hall reorientated the focal points to create a circular "crown" of plywood ribs above the stage, radiating out to include the organ.
"[Hall's] whole design was about allowing that organ to be the most prominent element in the space apart from the circular crown above the stage," Croker says.
"It's a very spectacular organ and, to see the inner workings of it, [is] just mind-boggling. It's a wonderful piece."
Although the organ is a crowning feature of the Concert Hall, it is only played about six times a year.
From a maintenance perspective, it's a very sensitive instrument, Jakubowski says.
"It requires a constant temperature and humidity to make sure it's performing at its best. It has be 22.5 degrees in the space, [with] a humidity of 55 per cent," he says.
During the recent upgrade of the Concert Hall, two layers and several hundred metres of imported sail cloth were used to shield the organ from construction dust and debris.
Ahead of the hall's reopening in July this year, the organ was also cleaned and tuned — painstakingly, one pipe at a time.
4. The house has an underwater workshop
Tucked away, underneath the northern boardwalk, is an "underwater" workshop where construction and repair works are carried out.
"We needed a space to create noisy works without disturbing artists, patrons and staff [who] work onsite," Jakubowski says.
Because the building is largely concrete, noise travels easily and can resonate towards the stage, "which would, in turn, disturb a performance or a rehearsal", he explains.
"So, we found this unique location underneath the precast panels of the boardwalk where we can cut up granite, cut down tiles — things that you wouldn't necessarily want patrons to hear or see," Jakubowski says.
Underneath the house is a "cathodic protection system", which essentially protects the master structure from corrosion with a "sacrificial" layer of metal that is more easily corroded.
Although subject to changes in sea level — especially during a king tide — the system prevents water from seeping in or flooding the workshop.
"The large seawater panels [or] cutting blocks that you see going into the water create the effect of the building sort of hovering on top of Sydney Harbour. Underneath that, the water can still flow up," Jakubowski explains.
"So, when we have king [or] high tides — or lots of ferries going past the building — the water will go up the cement slab underneath the building but then run back down."
The workshop is only accessible to Jakubowski's team. While the Sydney Opera House can have around 200 maintenance contractors and staff onsite at any given time, typically only two or three will be in the workshop.
"Being able to work with the sound of the waves and the wake of the waves touching the building is quite unique. It sort of feels like you're on a boat," Jakubowski says.
"It's the best workshop in the world."
5. The Concert Hall walls are 'tuned'
The much-maligned acoustics were a major focus of the Concert Hall's recent refurbishments.
In February 2020, the venue was closed for the first time in the Sydney Opera House's history and a team of world-class acousticians and architects assembled to correct its acoustic shortcomings.
Part of the solution they developed during the $150 million makeover was new, diffusive wall panels that are "tuned" to middle C, as Croker explains.
"If you were to generate a middle C from the centre of the stage and froze that in space, you end up with this diffusion pattern," Croker says.
Essentially, the curvature of the panels emulates the waveform of the middle C note, which is located, roughly, in the middle of a piano keyboard.
The panels have been installed over the flat surface of the sawtooth-shaped seating boxes. The major issue was that the boxes reflected sound directionally rather than diffusing the sound, as the new panels do.
"The original flat, sawtooth panels were just a straight musical note, and what you have now is a diffusion or an undulation on the front of the walls, which is very tactile — it's quite beautiful," Croker says.
In addition to 18 magenta acoustic reflectors installed above the stage, the panels help to bounce sound back to musicians on stage.
The renovation design team faced a difficult task in balancing the acoustic needs of the space while still maintaining the hall's heritage values.
"This was a really major change in the auditorium, and it was very contentious because the configuration prior to that was basically as Peter Hall had designed it, and … this was his most significant interior."
Croker says it was vital that the new design features aligned with Hall's original.
"[The refurbishment] changes those sawtooth pattern panels into a more organic, more vibrant pattern, but it's still the same timber — solid brush box — and it's got a very soft sheen to it. And it just works acoustically," he says.
"Ultimately, that's what we wanted to do: We wanted to achieve an acoustic result that would make this hall one of the finest concert venues in the world."
When the Concert Hall reopened and welcomed its first audience on July 20, Croker knew the project had been a success.
"The sense of anticipation and excitement at that performance — I don't think I'll ever have again in a performance. It was just extraordinary," he says.
Episode one of Inside the Sydney Opera House is streaming on ABC iview. Episode two airs October 30 at 7.30pm on ABC TV.
