Water channels dug by convicts, rail tunnels to nowhere, one-way passages from court to the gallows, coal mining under Sydney Harbour – a buried history of the 19th and 20th centuries winds beneath the bustling feet of 21st century Sydneysiders.

While we may take pride in ours as a city surrounded by water, the land is built on a honeycomb of tunnels, their mysterious secrets haunting the subterranean depths. So here we donned our boots and prepared to muddy ourselves deep in time.

The Tank Stream

The story of the Tank Stream is also the story of how Sydney’s city came to be established where it is. In 1788, Captain Arthur Phillip was searching for a fresh water supply around which to build his settlement. He found a stream running into Sydney Harbour, sourced from a swamp located between where Hyde Park and Town Hall stand today, as well as from a couple of springs. Closer to the harbour at the stream’s high tide, small boats could come much further than present-day Circular Quay, getting as far as the road that would come to be called Bridge Street, where swamp and spring met salt water.

This stream became virtually the only source of the colony’s water, and the site of the first social divide among the European arrivals. Convicts lived on the western side – so too would boy orphans – while government buildings were placed on the east. But 1789 and 1790 proved so dry that the flow slowed. Philip ordered the convicts to cut three tanks beside the stream for storage, giving the Tank Stream its name.

But Sydney’s first white inhabitants weren’t so eco-minded; indeed some farming and slaughterhouse settlers were more foul than fair. Some people were observed washing naked in the stream near the King Street area. In 1803, with the colony’s population around 6000, a notice was placed in the Sydney Gazette, which read ominously: “If any person whatever is detected in throwing any filth into the stream of fresh water, cleaning fish, washing, erecting pigsties near it or taking water out of the tanks on conviction before a magistrate their home will be taken down and forfeit five pounds for each offence to the orphan fund.” Convicts fouling the water were flogged.

In 1826, having become a virtual open sewer, the stream was abandoned. For the next 11 years, the colony’s drinking water came on carts from the swamps, until Busby’s bore opened in 1837 [see below]. The Tank Stream was diverted under Pitt Street in 1858 and over the next few years covered with sandstone culvert.

Today, Sydney Water conducts twice-yearly Sunday morning tours in a small portion of the Tank Stream. The tours are popular and participants drawn from a ballot get to wear hardhats and gumboots and walk through a 200-metre section of the tunnel below Hunter Street.

At one point, the ceiling is no more than 1.5 metres tall, so almost everyone has to hunch over. The tour only lasts 25 minutes, but there is an aura to being down here: convicts’ initials can be seen in the sandstone blocks, and there is a 150-year-old iron pipe running through the ceiling; one of Sydney’s first sewers. The trickle of water beneath our feet in these damp and dank confines is only stormwater; sewage was long ago diverted via pumping stations to Bondi.

On a recent visit to advise the City of Sydney on how to maximise its public spaces, Danish urban planner Jan Gehl suggested the city make greater use of its water features such as the Tank Stream, even advocating that parts of the Tank Stream be brought to the surface. But not everyone agrees. Tony Gilmour, the author of Sustaining Heritage, Giving the Past A Future (Sydney University Press, 2007) says opening the Tank Stream would mean losing some impressive stonework, and the stream runs under so many buildings that there are few spaces left in Sydney free for a re-created river.

“My fear would be that it would become a sanitised, pretty water feature telling little of its story,” Gilmour says. “Recreating an open sewer would be authentic, but not too popular! I’d keep the stream covered but expand and develop the tours underground, [like in] Paris and Istanbul.”

The water trickles on in the tunnels, as does the debate.

St James tunnels

In the inky darkness, we sweep torch lights side to side and slosh through sludgy earth in Sydney’s great unfinished eastern suburbs subway – which would never actually see a train, but instead become an air raid shelter.

Thin tree roots drape from the ceiling and glisten in the spotlights like spiders’ webs; thicker roots that long ago sprang through wall drainage holes twist across our path. Could these gnarly tendrils really belong to the old Moreton Bay figs guarding Hyde Park above?

Some 40 metres south of St James station, passing under the Archibald Fountain, the tunnel divides into two single-track tunnels, both slowly snaking south-east, crossing literally over the top of the city outer rail line that after more than 80 years continues to carry trains deeper south-west from St James to Museum station.

But we hear not a thing except for the occasional dripping water and our voices; no scrape of wheel on steel, no carriage rumble. These subterranean burrows are dreamily quiet. I stifle yawns, pondering how much air is down here beneath the figs.

In 1926, St James station opened, after Hyde Park’s belly had been bisected like an open-heart patient to create a rail underground loop. Engineers had intended continuing these two eastern suburbs single-track tunnels right underneath Oxford Street, snugly following up to the Darlinghurst Court House – picture Taylor Square with a subway station – where one tunnel would have continued to Bondi Junction, the other to Randwick, says historian John Oakes in Sydney’s Forgotten City Railways (Australian Railway Historical Society, 2003.)

Instead, after planners and politicians disagreed on the route, work on the eastern suburbs tunnels was abruptly halted close to the ANZAC Memorial. During World War II, the tunnels were converted into a public air raid shelter, which Sydneysiders thankfully never had to press into service. Brick dividing walls were added to create smaller bomb shelter chambers. Australian Imperial Forces officers stationed down here scrawled their messages that can still be seen, including their regiment number and the date, many in 1942.

We step into a rectangular chamber flooded in ankle-deep water, in which stands a rustic steel bell with a pointy top almost as tall as a person. One of our group whacks the bell with a plank of wood: the gong sound is deafening. Sydney sound-sculpture artist Nigel Helyer created and installed the work, known as An UnRequited Space, as part of ArtSpace Sydney’s Working in Public project in 1992, employing a wooden mallet “to sound out the midnight chime on ABC National for 21 consecutive days”, Helyer says. Memo to the ABC: your microphone cable missing for 16 years is still connected between the bell and wall down here.

The fight over the eastern suburbs railway line dragged on for half a century after these tunnels were abandoned. Finally, in 1979, a very different line, running from Martin Place to Kings Cross and Bondi Junction via the Woolloomooloo viaduct, officially opened.

We take our torches north of St James station, where there is yet another unused tunnel, this one running beneath Macquarie Street – and this passage only deepens the mysteries and myths of Sydney’s tunnels. In 1928, chief railway commissioner James Fraser announced that, to reduce congestion on the main Sydney to Strathfield line, this unused tunnel at St James would take trains to a new western suburbs railway line via Town Hall, George Street, the old Grace Brothers store on Broadway and Sydney University, right up Parramatta Road.

But the plan quietly died. This long abandoned St James northern tunnel still houses an old signal box, and in the mid-1980s was the home of a train used to carry out asbestos removal from the rail network.

As we trek north, the air becomes more humid. We climb up a rickety metal ladder through a hole only half excavated and slip down a muddy embankment, meeting the edge of “Lake St James”: the drainage system of the city outer tunnel next door, the water stretches left and out of sight for a kilometre, 10 metres wide and about five metres deep.

The NSW Government says it aims to collect rainwater in tanks from the roofs of Parliament House, the State Library and Sydney Hospital, store the water in Lake St James, and recycle it back through the non-drinking system. Well, you certainly wouldn’t ingest this stuff, its fine film of brake dust floating on top.

The lake is home to an eel named Eric: “I’ve seen him, but no-one believes me,” one CityRail employee says. He spreads his palms a metre wide. “He’s about so big. An albino!”

If one had a canoe, one would find a room at the tunnel’s end which rumour has it was a bunker for General Douglas Macarthur. Sydney’s The Sun newspaper lent this legend weight in a report on a 1968 fire that broke out in the tunnel in a vertical shaft that once contained a staircase leading up to Shakespeare Place, north of the State Library. This shaft “was reported to have been a secret military headquarters used by US General Macarthur during World War II,” the newspaper claimed.

The legend is not entirely silly: the unused tunnel does pass beneath the city inner track, which runs under the Royal Botanical Gardens, between the Mitchell Library and the Conservatorium of Music, and, according to John Oakes’s book, the Royal Australian Air Force secretly based its anti-aircraft operations in rooms off the city inner track for six months in 1942 after the Japanese midget sub attack on Sydney Harbour, unbeknown to train commuters.

These stories spark more questions: how many secret rooms, shafts and chambers were there? Sydney surely had more tunnel byways, only to quietly cover over much of its subterranean history.

Georges Heights and North Fort tunnels

Sydney’s harbour defences began small, with a gun pit placed at Obelisk Point at Middle Head in 1801, a couple of years prior to the Napoleonic wars. “But it was only a little fella,” says Sydney Harbour Federation Trust volunteer guide Mike McBride of that first battery.

Following the 1850s Crimean War, Sydney took tiny Pinchgut Island, once an isolated place to dump convicts near Mrs Macquarie’s Chair at the Domain, built a fortification to protect us from Russian warships, and renamed it Fort Denison, after the then NSW governor. Finally, by 1870, when British garrison troops began withdrawing from Australia, work on “outer” harbour defences at last got cracking, a rabbit warren of tunnels dug out at Middle Head and Georges Heights.

McBride stands on the Georges Heights lookout, a magnificently preserved set of tunnels under his feet. “You can see what a tremendous spot it was to defend everything,” he says. “You can command the whole area, the whole entrance to Sydney Harbour. Engineers and gunners were here until right after the Second World War.”

Except the whole outer defence system would eventually fail Sydney. In May 1942, a Japanese reconnaissance plane was spotted at Georges Heights, but mistaken for an American Curtiss Falcon floatplane due to false markings.

A day later, despite the addition of a submarine net between Georges Head and Green Point and new quick firing guns, the Japanese were able to fire three midget submarines just 11 kilometres from Sydney Heads. One midget submarine became entangled in the net, yet two made it into the harbour; one running aground, the other releasing two torpedoes – one successfully striking beneath the HMAS Kuttabul on June 1, sinking the ship and killing 19 Australian and two British sailors.

McBride leads us through two substantial Georges Heights tunnels, named by the Army as A84, built in 1872, and B42, built in 1877. The temperature drops several degrees down here. The rough, sharply zigzagging passages might have potentially helped protect gunners take shelter from a blast, but one wonders whether the design would have slowed everyone down when springing into action, or had they needed to escape.

“We all got lost, the first time we came here,” McBride admits. In A84 there is a white-tiled hospital room, which never saw action. Cavities in the walls for kerosene lamps are a reminder of the age of these tunnels.

In B42, the air is especially damp and dank. Bogong moths scatter under torch beams. A metal dumbwaiter hangs from the ceiling in the original cartridge store; it was used to haul ammunition up to the guns above. We switch the electric lights off and the natural light through the ceiling casts an eerie glow around the dumbwaiter to form what looks like a moon eclipse on the tunnel floor.

Over the late 19th and early 20th centuries, these tunnels were also the bases from which signallers and engineers could by remote control detonate submarine mines laid around Chowder Bay below, even before Sydney homes had electricity. Cable marks can still be seen on one tunnel wall.

Early on, it went horribly wrong. On Friday April 3, 1891, while preparing for a display of destruction of aging mines for the NSW Governor, defence officials and the public, a cabling mix-up accidentally detonated a charge on the side of the boat carrying explosives. The horrified crowd watched as the boat blew, sending eight oarsmen and five submarine miners flying into the water. Four men died.

Fifteen minutes up the road at North Fort at North Head, now part of an artillery museum open to the public, we traipse through a beautifully engineered cylindrical 300-metre sandstone 1930s defence tunnel. “Considering it was 70 years ago, it’s probably the best engineered tunnel in Sydney; for its day, anyway,” North Fort business manager David Leyshon says.

“Above the steel girders here there’s approximately a meter of concrete, and then compacted earth on top of that. So the idea is if Australia was being attacked from sea during war, and a shell came in, it wouldn’t have gone through the concrete.

“Nowadays, of course, a missile would go through anything.”

Midway through the tunnel is a green door. We’re not allowed to have a look behind it. Rumour has it the tunnel is still in use – for anti-terrorism exercises – but Leyshon refuses to comment. “Despite what anyone might tell you, we don’t have an underground hospital, and there isn’t a tunnel between North Head and South Head,” he says. “No, no, no, no,” he emphasises.

Guns shipped in from Glasgow – big enough for 32 men to sit on, as one photo in the museum shows – were installed above this tunnel during World War II; these could traverse 360 degrees and thus fire anywhere.

After the war, Leyshon says, prime minister Bob Menzies ordered the guns be cut up for scrap, “because a gun that could fire 30 kilometres couldn’t defend itself against a rocket.”

One remarkable curiosity about this tunnel: water flows along both sides of the raised tunnel path; it travels here underground from the Blue Mountains. The sound is strangely comforting. Leyshon says the water is 99 per cent pure and worth bottling.

“We approached Coca-Cola. They came along, did a study, worked out how much there was, decided it wasn’t enough, and said ‘thanks, but no thanks’.”

More tunnel tales
Busby’s bore: In 1824, when the Tank Stream had become very polluted, mineral surveyor John Busby was engaged to find an alternative. Completed on the backs of convict labour in 1837, the 3.6-kilometre water tunnel, 1.2 to 1.5 metres wide, had the capacity to supply Sydney’s then population of 20,000 with 1.5 million litres of water a day, drawn from Lachlan Swamps – later called Centennial Park – underneath Victoria Barracks and down to Hyde Park. It remained in use only until the 1880s – most of the tunnel remains intact today, apart from a small section underneath Oxford Street that was filled with sand in 1934.

Hero takes a fall: Sydney’s oldest hotel building, the Hero of Waterloo pub in The Rocks, built in 1796, had a trap door operated by the barman in its early days, Brian and Barbara Kennedy report in their book Sydney Tunnels (Kangaroo Press 1993). Unsuspecting drunks, runs the local legend, would then drop to a cell “to be sold later to some ship’s captain who was looking for crewmen.”

Balmain gold: Was Sydney centred on a continuous coal basin? In 1878, a title to mine under Sydney Harbour’s waters was granted to find the answer. And yes, Balmain’s own coal mine, known as the Sydney Harbour Colliery, opened to the north of what is now the Birchgrove Primary School, in 1897 – but never quite managed to extract enough coal to meet costs, finally closing in 1931. In 1924, a letter writer to the unions’ Labour Daily newspaper described the cage used to lower 36 men at a time as a “living tomb”: “Much of our risk could be remedied, but profits stand in the way.” Attempts to bore below the mine for gas resulted in explosions in 1933 and 1945, killing four men in total. In 1957, the shafts were filled with ash and concrete, and most of the workings today are “probably filled with water”, according to the NSW Department of Primary Industries: “It is considered impossible for an explosion to occur.”