About 76,000 Allied soldiers and civilians were marched through the old Changi Prison's gates for internment as prisoners of war during World War II.

Thousands were packed into the facility which was designed to hold just 600. The internees suffered from overcrowding, malnutrition and diseases such as beri beri and malaria. Food was in short supply and they turned to wildlife, such as sparrows and rats. The prison, designed by the then Public Works Department as a maximum security prison, was originally built within a 6m-tall perimeter wall.

It comprised two four-storey blocks of prison cells branching out from a central covered corridor that allowed wardens easy access.

But Changi Prison was demolished in 2004, and in its place today is the Changi Prison Complex.

Heritage lovers have lamented the loss of the old Changi Prison and, prior to its razing, Australian leaders had called for it to be saved as about 15,000 Australian soldiers had been held in the Changi area.

Associate professor Anoma Pieris, an architectural historian from the Melbourne School of Design with a specialist focus on South and South-east Asian architecture, believes "it was a question of international more than national heritage".

"Contemporary citizens of Singapore view Changi as a civil prison and an unlikely object for preservation - that is why there was no great public uproar about its demolition."

But some parts of the old prison were preserved, namely its entrance gate, a 180m stretch of prison wall and its two corner turrets.

They were collectively gazetted as Singapore's 72nd national monument earlier this year by the National Heritage Board's Preservation of Sites and Monuments division "in remembrance of Singapore's wartime experience and as a grim reminder of this dark episode in our history".

Melody Zaccheus