Secret tunnel in harbour cliff face rediscovered

CARVED into the side of a mammoth cliff face beneath a lighthouse on Sydney’s Harbour is a site buried long ago in the pages of history books. Until now.

A TINY tunnel, embedded in the cliff face below a Sydney Harbour lighthouse has been rediscovered using state of the art 3D mapping technology.

Ahead of the 200th anniversary of the Macquarie Lighthouse in Sydney’s eastern suburb of Vaucluse this year, researchers from Macquarie University were approached by the Sydney Harbour Trust to create a ‘digital gift’ to mark the occasion.

The university’s senior learning designer, Michael Rampe, told News.com.au that he had learnt of the hidden tunnel during a planning meeting with the Trust in May.

“During this meeting they told us they had heard about an emplacement on the cliff but that very little was known about it,” Mr Rampe said.

“The Trust didn’t even know where the entrance was and asked us if there was anything we could do to help find it”.

The secret WWII tunnel (circled in red) was rediscovered using drones by Macquarie University. Picture: Macquarie University

According to members of the Trust, the tunnel was known to very few people but was believed to have been built in World War II and forgotten for decades.

Taking up the challenge, Mr Rampe used a range of technology to capture all angles of the Macquarie lighthouse and it’s surrounds in order to locate the tunnel’s entrance.

The team took 3D scans of the lighthouse, launched drones to capture aerial footage of the site and activated terrestrial laser scanners and ground penetrating radars.

Close up recreation of the secret tunnel entrance. Picture: Macquarie University

It was during a drone deployment that the team located the tiny, rectangular entrance to the tunnel.

“We flew the drone down and made sure to pay careful attention to the area,” he said.

“The first day we went was very windy but we managed to find the entrance and get some good images.”

The second day of the expedition saw the team take an “exception drone pilot” to get close-up imagery of the tunnel as well as the rest of the cliffside.

Using photogrammetry — a form of 3D modelling — the team then pulled together all of the footage to create a 3D mapping tour of the Macquarie Lighthouse, with the secret tunnel clearly visible on the cliff face.

Screengrab of the 3D map of the Macquarie Lighthouse cliff face, in which the secret WWII tunnel was constructed. Picture: Pedestal 3D

But what exactly was the tunnel used for?

Mr Rampe says there are many accounts of what purpose the tiny tunnel may have served.

“The current theory is that it was originally a searchlight spot and that’s what we believe it to be at the moment but we’re working on verifying that,” Mr Rampe said.

And while the general consensus is that the tunnel was constructed in the 1940s, around WWII, the team have also received some anecdotal evidence to the contrary.

“Just today, someone called us to say they remembered their grandmother visiting the tunnels there back in 1919, which predates the Second World War,” he said.

“It may well have been built earlier and repurposed later on”.

The Macquarie lighthouse will celebrate 200 years since its construction in November. Picture: Sydney Harbour Trust

The team is preparing to head back to the lighthouse to use radars after receiving a tip-off that the tunnel could be one of many etched into the cliff face to form a network.

“We have been told there are quite a few tunnels and we may well find the entrance to some of those on our next trip out there,” he said.

“We aim to go back with our ground penetrating radar to have a closer look at a few areas of interest.”

The Macquarie lighthouse will celebrate 200 years since its construction in November. Picture: Sydney Harbour Trust

For Mr Rampe, the evolution of 3D mapping technology has allowed for the rediscovery and preservation of a key part of Sydney’s history.

“We believe there is a need to open historical sites like this digitally to access things that otherwise may not have been possible,” he said.

“Our work is normalising 3D technology to help people across the country, and the world, to experience cultural heritage sites.”

The team from Macquarie University will unveil the remainder of their photogrammetry project and their findings during the 200th anniversary of the Macquarie lighthouse in November.

The Macquarie Lighthouse will also be able to be climbed during the celebrations on the weekend of November 3-4.