Standing on the Royal Botanic Gardens culvert, it is almost possible to imagine the wife of Governor Macquarie taking a stroll across the elegant little bridge she designed nearly two centuries ago.
Ignore the skyscrapers that tower over the hodgepodge of exotic trees and the fact that the shoreline was over 100 metres to the north.
Picture instead what life was like in Sydney when building a few kilometres of road was a profound act of civilisation, and before any colonist had the slightest clue what lay on the other side of the Great Dividing Range.
Mrs Macquarie's road once snaked from Old Government House through to Mrs Macquarie's Chair and was completed on June 13, 1816.
History records that the craftsmanship of the convicts was rewarded with five gallons of spirits.
However, today the only stretch known to remain is on top of the culvert over the Royal Botanic Gardens Creek. It is one of the oldest-known sections of road in Sydney, but its existence surprised archaeologists and heritage architects from the Department of Public Works and Services when they began to dig under a walkway.
A joint team from the Royal Botanic Gardens and the department was charged with restoring and conserving the culvert, which was readily visible by leaning over the rails beside the track over the creek. Nearly all the mortar had been washed out from the brickwork holding up the arches. Also, the roots from one of the garden's rarest plants, a 120-year-old giant fern, was slowly strangling the historic culvert.
The gardens' acting curator, Ian Innes, said: "We were as keen to protect the plant as we were to protect the culvert."
During exploratory excavations the team discovered that the original road across the culvert lay beneath two centuries of sediment.
As soon as the old road was found a decision was made to seal it again under a layer of asphalt so that it remained intact for future generations.
Stonemasons used the remaining bricks and original convict bricks obtained from a gardens stockpile to repair the culvert and return it to the rock-solid structure it was when Mrs Macquarie used it.
"The best thing is that the culvert is not high and dry in a museum," Mr Innes said.
"This is still working as a culvert."
Joy Singh, a heritage architect with the department, said the restoration included retrieving a rare block of a rock called trachyte - which had originally been quarried at Bowral - from the bottom of Sydney Harbour so that it could be used at the base of the culvert.
"The culvert should last at least another 100 years," Ms Singh said.