Shirley Fitzgerald confesses to "a sort of a weakness". "When I'm on my own I sometimes practise trying to move through the city as if it was the 1920s or the 1880s, or whatever. I can't do it with great precision, but it's fun to strip away what is there now and think: what would this walk have been like if I'd done it then? Because there's a million cities."
There's even the city before it was a city, before roads lay over the top of bush and beach. Fitzgerald in time-traveller mode thinks of it whenever she walks into Customs House at Circular Quay, as she will today fortnight to give a talk for History Week, Ebbtide: The Harbour In Sydney's History .
"The City of Sydney owns that building, which is the point where Phillip came ashore and raised the flag … Every time I go into that building I realise I'm stepping over the shore, because it would have been filled in there," says Fitzgerald, the City of Sydney historian for the past two decades. "If you look at the paving, you can follow the shoreline. There are different colours. Sydney's been hewn down and carved up and raised up, amazingly, but the first major rearrangement of the sandstone was the filling in of that estuary to build Circular Quay."
In the years since she wrote her history of Sydney for the celebration of the city's 1992 sesquicentenary, her head has been filling with the layers in time and space that have made our metropolis.
"The eye which is attuned to the way in which the city has developed will find endless traces - the faint outline of an ancient rock carving, or an old sign advertising a product or a political cause, some worn steps, a balustrade, a ring embedded in a wall where once a fisherman hung his nets to dry, remnants of a tram line shining through a break in the bitumen road surface," she has written.
Not everyone wants the layers revealed. To Fitzgerald's disgust, Abe Saffron threatened to sue when he learnt he would be mentioned in one of the 100 street plaques she instigated to tell the story of Darlinghurst Road. On legal advice, the council withheld the plaque until his death two years ago. Now in place, it notes he had "friends in high places".
But sophisticated new plaques are soon to come across the metropolis. With a tap on their web-connected phones, passers-by will be able to turn time travellers by downloading information from an online Dictionary of Sydney when they see any city landmark marked with a symbol.
The dictionary, due to go online late this year or early next, already has hundreds of entries as volunteers across Sydney's 600-plus suburbs write contributions. Because it is on the internet "there is no end to it", with potential maps, music and other flourishes explaining the stories, says Fitzgerald. As chairwoman of the dictionary's board of trustees, she describes its breadth as "scary".
It will reveal stories not only of buildings, but of protest marches, traffic accidents and people.
"The Encyclopaedia of New York had an entry on the Twin Towers and by the time I read it, they had gone. Cities change. They're dynamic, and the electronic version does allow you to adapt, change, alter, add in or archive, as there is a new understanding or theory," Fitzgerald says.
The City of Sydney council has donated about $120,000 a year for five years, and the Australian Research Council has provided a $1 million grant through Sydney University. "Here at the dictionary, we oscillate between euphoria and hysteria … It's the most exciting thing I've ever been involved in," says Fitzgerald.
That may be an overstatement. Fitzgerald has had plenty of excitement in her life, thanks to a radical streak, a dry sense of humour and a feisty insistence on her right to speak out as a citizen, despite being a public servant. "Sometimes when I speak, I'll get into trouble for it. But I see little sense in devoting your life to try and understand and work with the history of a city and then not be prepared to share that with people at times of major stress."
To her, the key question is: "Who gets access to this rare piece of urban dirt? A city is a very competitive place, where the people that win and the people that lose are what fascinates me."
A one-time political ally of the former Builders' Labourers Federation head Jack Mundey, who led the 1970s green bans movement against over-development, she laments the Sydney mentality of "trash it when something better comes along".
The city has too many Harvard MBAs who think the bottom line is only economic, she says, when it is perilous to ignore cultural consequences and sense of community.
At Pyrmont in the 1990s, she spoke out for residents who felt powerless against developers' subdivisions aimed at a "high-tech and ritzy" suburb where workers once lived beside the factories, wharves and woolsheds in which they toiled. Plans for the casino left her aghast.
Fitzgerald has a strangely diffident air at first meeting, but the ebullience of the enthusiast bursts through. She has the admirable ability to surprise.
Historians often feel like frauds, she says. "I know I do. Because when the history is written, the historian knows that the task is not completed. There's no end to what happened in the past. The only thing that's bigger than the past might be the future and we don't even know that for sure."
On the other hand, she describes the breast cancer she suffered 10 years ago as "a great gift, because you realise life is a great gift".
"It's very confirming because I realised I didn't care about whether I had my breast hacked around or not. That was reassuring to know that it is not how I defined myself … The whole business of being very sick and very vulnerable did turn into a positive - grab life and get on with it."
Fitzgerald was born 59 years ago on Kangaroo Island, where her father was a schoolteacher. Her two great memories are of the school bus which gathered up the pupils and the wind generator that provided her family with power. "Right from the beginning I had the public transport thing and the alternative energy thing happening in my backyard."
She sees these threads in her children. Her daughter Kate Fisher, 33, is a photovoltaic engineer in New York working to make solar cells more efficient, and son Tom Fisher, 31, is involved in planning cycling tracks for Armidale council.
Fitzgerald adopted our showy metropolis more than 30 years ago when she did her doctorate at Macquarie University on environmental degradation and social mobility during Sydney's late 19th century rapid growth. It became a book, Rising Damp .
She gives genuinely funny speeches. She once told of Pyrmont residents naming a little park Yuroma, thinking it meant "spirit of the fig tree". Her research found one source defining it as a fierce fig-dwelling spirit warding off intruders "by a menacing demeanour involving the threatening use of its genitals".
"Great name for a park," she says.
Fitzgerald insists professional historians are better researchers because they work constantly with records. She smarted when a judge decided he was more expert at deciding past events in a court dispute over use of laneways.
Her wit can verge on withering sarcasm. She has had many "interesting" conversations with politicians who, like the former premier Bob Carr, consider themselves historians. "They do consider themselves to be politicians first and they do consider that they are the ones who should be making the running on things … People who have convictions about things are the most difficult to deal with as they are the ones least likely to give anybody else professional space to have views in those areas," she says.
In the 1990s, Fitzgerald incurred Carr's displeasure for passionately and publicly opposing government plans to demolish wharfs 8 and 9 at Walsh Bay. She agreed to appear for the National Trust as an expert witness but Carr brought an end to the court case on the day it was due to start by making his planning minister, Andrew Refshauge, the consent authority for Walsh Bay.
An escape? No, says Fitzgerald. "There was a certain amount of wrath. At the time I was serving on a government board - the Historic Houses Trust - and I think I may have the honour of being the only person to serve on that trust who never had a second term offered to them." She says she has not been censored by any of the five lord mayors in her time as city historian.
She needs occasional respite, however. Her bolthole is an unrenovated fisherman's cottage at Huskisson with her partner Tim Peach. It is no-fuss 1950s: "No television, no carpet, no nothing really." The escape is temporary. "I haven't found any bit of Sydney that's bored me yet," says Fitzgerald.