In a heaving metropolis like Sydney, they're about as secret as you can get.

Perched on the cliffs above the harbour and surrounded by thick bush is a cluster of empty huts few know about.

But people who want to protect the heritage-listed buildings, which date back to the 1920s, say their future is at risk.

On the day the ABC visited, rubbish and even human faeces had been left on the ground around the huts.

"What a mess, that's really sad to see," says Alida Hazelgrove, who has a long history with the site as a visitor and is advocating for their protection.

The huts offer great views, but their location is not promoted. ( ABC News: Mridula Amin )

Toilet paper covered in human faeces had been left on the ground around the huts. ( ABC News: Mridula Amin )

Alida is using the 100th anniversary of the huts' construction to put the spotlight on their management, saying National Parks and Wildlife Service (NPWS) needs to stop putting the huts in the "too hard basket".

At the "entrance" to the almost village, one sign says "do not enter", but another reads "welcome ... enjoy".

It's a contradiction that sums up the current debate.

The huts are largely untouched and unknown and the NSW Government wants to keep it that way.

It's impossible to find them without insider knowledge.

A deliberately secret location

The huts are frozen in time and offer a peek into Sydney's history. ( ABC News: Mridula Amin )

With respect to the NPWS's wishes to protect the heritage of the huts by not publicising them, the ABC will not reveal the exact location of the huts.

After evicting squatters in the 1980s, the Government chose not to demolish the huts, but also not to advertise their presence, in the hope of keeping vandals at bay.

The decision to keep the site a secret has allowed NPWS to manage the site informally and focus on maintaining the fragile huts they say could be "loved to death".

There is no signage to mark the rocky track to the huts. But there are no fences either.

Inside one of the huts. ( ABC News: Mridula Amin )

Squatters moved into the huts in the 1960s. ( ABC News: Mridula Amin )

Volunteers conduct patrols, but it's not known how often, and in one of the huts' windows a crumpled sign dating back to 2014 says vandals have been in the area.

Although photos on the internet indicate NPWS had a more open-door policy in the past and people could enter the huts, they are now locked and almost every window is blocked, some with timber, another with a NPWS T-shirt.

A spokesperson for NPWS told the ABC there were fears the huts could fall victim to the vandalism and illegal activity which has overrun some military bunkers in Sydney.

But Alida says the current approach to managing the site neither keeps vandals out nor educates people about the rich history behind the huts' walls.

"It's a shame you can't trust a lot of humans, but it's obvious people who trek down are curious."

Alida Hazelgrove looks on while sitting outside one of the huts. ( ABC News: Mridula Amin )

The exterior of one of the huts. ( ABC News: Mridula Amin )

Alida, who visited the huts almost every weekend in the 1980s and knew some of the squatters, said she feels torn as she doesn't want the site to "become a toilet" but also doesn't want it shrouded in mystery.

"It can't just be this giant question mark, because that's what it is at the moment," she says.

"This 'we won't look at it and maybe it will go away' approach isn't working."

Originally built as basic fishing shacks in the 1920s but transformed into homes during the Great Depression and again in the 1960s, the huts embody what it means to escape.

"It was as though you were travelling away from the normal world into a magical place … total privacy," Alida says.

The squatters who moved in during the 60s enjoyed an idyllic unregulated existence among nature, but they were evicted in the 1980s when the NSW Government declared the land a national park, a decision upheld by the courts.

A closed sign outside one of the huts. ( ABC News: Mridula Amin )

Those living nearby who resented the 'hippies' living rent-free with million-dollar harbour views were pleased, but for the squatters it meant leaving behind an oasis they had nurtured.

They may have been deep in the bush but it certainly wasn't primitive living; rainwater infrastructure was built, solar panels were installed and beautiful carpentry made the huts works of art.

The stacked tea cups and made-up beds which are only just visible through one hut window offer a glimpse into the simple pleasures the squatters enjoyed.

Alida hates to think her friends' stories will be lost to time and wants NPWS to erect signage and organise tour groups so visits are encouraged but controlled.

She is adamant increased traffic wouldn't take away from the serene feeling she gets when walking from hut to hut.

"It won't lose its feeling because that's in the bedrock of the place."