The prison, built in 1842 by convicts (the ultimate do-it-yourself project), had operated as a maximum security facility until 1991.
Prison stationery, old arch files, even a coffee cup still sit in the administrative office - it's as if the officers had walked out just yesterday.
Our guide is James, a small man with a luxuriant waxed moustache and a sense of humour so dry it almost crackles.
From the prisoners' reception area we pass through the white-tiled shower room - it's spartan but no worse than many sports club shower rooms.
A door on the other side of the showers led to a central courtyard - scorching in the Western Australian sun, the light blinding on the limestone.
The modest size of the prison entrance belied the scale of the facility - the main block was vast, storeys high. Far to the left, beyond a wall, was another high roof - it had once housed female prisoners. To the right was the remains of the quarry that had yielded much of the stone for the construction work.
James led us inside the main block.
Prison cells opened up off both sides and above us were two more floors, accessed by a wired-in staircase and narrow walkways.
A net stretched across the entire width of the block just above head height.
"The suicide net" James explained.
He held up the bucket that was the only toilet facility for each two-man cell for most of the day.
"Have a guess why the guards always walked around directly under the walkways? " he said.
Fremantle Prison is shortly to be granted World Heritage status and on this ground level, a series of cells have been restored to illustrate prison conditions since the first inmate arrived in the 1840s.
There were no beds at first, just hammocks, and at one point cells had toilets, until the stench from the drains became too bad even for a prison and they were removed.
One contemporary cell was covered with paintings - one prisoner had been granted permission to decorate his cell as a form of therapy.
The entrance to the chapel was from the second level.
Bright light streamed in the tall arched windows. Behind the sanctuary a prisoner had painted The 10 Commandments, the Nicene Creed and the Lord's Prayer.
James pointed out that the sixth commandment had been changed slightly from: Thou shalt not kill to "Thou shalt not murder".
Attending church was a popular activity, James said, although for many men it was not anything to do with their spiritual wellbeing.
An upstairs gallery seated women prisoners from the adjacent block.
"Can't you just see the women peering over the railing saying "'Ah men?'" he asked. The overseas tourists looked bemused.
The kitchens and scullery were on the ground floor. Working in the kitchens was sought-after work for prisoners, not the least because when they weren't at work, they could watch television, or listen to music in an adjacent room.
This room had once been the prison bakery. There was a photo of the brick oven, two inmates unloading bread from it.
"You'd never eat the bread here," said James, who'd seen me looking at the photo.
I asked why, "You just don't want to know what the prisoners put in it," he said. It was my turn to look bemused.
"Look, if you knew everything I did about what went on in here you'd go home, take a long, long shower and then burn your clothes," said James with surprising vehemence.
Was James a former "screw"? I didn't like to ask - the man had the keys.
Beyond the kitchen was the exercise yard. Three or four-metre-high walls topped with razor wire formed a rectangle together with the wall of the prison block itself. In the centre were a few benches and tables shaded by a metal canopy.
This had been a prison improvement only late in its existence.
Previous prisoners spent almost all their waking hours in this yard, unprotected from the heat which could soar to more than 40 degrees.
They were watched over by a guard in a metal cage - if a fight broke out he watched and took notes but never interfered. It would have been one man against many.
Just before the prison was closed, prisoners who wished to were allowed to paint murals on the exercise yard walls. Outback sunsets, graceful eucalypts, kangaroos. The paintings were devoid of any sign of human activity.
James showed us where prisoners were flogged, and invited everyone into the darkness of the tiny solitary confinement cells.
I watched as the German-speaking parents of two boys aged about three and five, carefully translated all of James' explanations, complete with actions.
I hoped they'd refrain from doing so when James reached the gallows. Forty-four prisoners had been hung in there.
I didn't find out firsthand - there was enough violence and misery seeping from the ordinary prison walls without venturing into the execution room.
I waited for the group in the office block. And yes, I was told the parents had given their boys the full translation - I hoped they were made of sterner stuff than me.
As we left I said to James that I'd guessed what had gone into the bread.
He told me I was right. For a few days at least a no-carbs diet was looking good.
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