A former chemical weapons factory where British scientists contributed to early atomic bomb technology should be preserved, experts are to say.
The site was 'pivotal' to the allied war effort
The Valley Works at Rhydymwyn, near Mold, Flintshire, produced hundreds of tons of mustard gas in World War Two.
But its history goes back to the 18th Century, according to university researchers who studied the site, now a nature reserve, for five months.
They are to present their findings at a public meeting on Tuesday.
Experts from Birmingham University's school of archaeology were commissioned to examine the industrial heritage at the Flintshire site.
The work included evaluating the atomic bomb research, codenamed Operation Tube Alloys, which made the site one of Britain's greatest wartime secrets.
Many of the scientists who worked on Operation Tube Alloys, were sent to work on the Manhattan Project, which developed the first atomic bomb, according to Kirsty Nichol, the survey's project manager.
She said the buildings put up to disguise the chemical weapons also being made at the site should be kept.
She said: "It is hugely important. Because of the tube alloys project, these type of structures do no survive anwhere in England from this period.
"It's not a particularly nice thing to think about - chemical weapons to kill people - but in terms of the wartime mentality, when everyone had their own gas mask, it touched the lives of an awful lot of people in the UK."
Rhydymwyn has been open to the public as a nature reserve since 2003, but its history could be traced back to a foundry in 1747, and at one point the site was used to make watermills, said Ms Nichol.
Her team's findings are presented to the public at 1900 BST on Tuesday.
Site manager Grant Webberley said: "This is a detailed study which looks back before the site became pivotal to the allied war effort.
"But it is as much about looking forward as looking back, and the report makes recommendations as to the future of the site."