The leader of Bolton Council, Cllr Linda Thomas, joined founder members of the Octagon Theatre on a tour of the redevelopment site.
Gerry Russell and Dr Phillip Butterworth were two of the five students who laid plans for a new theatre in Bolton, along with their drama lecturer Robin Pemberton-Billing,
Taking only seven months of construction, the theatre was officially opened on November 27, 1967 by Princess Margaret.
Work to update backstage facilities, improve accessibility and create more space for community involvement is being carried out by Wilmott Dixon.
Dr Butterworth said: “As you might imagine, this was a nostalgic and inspiring tour conducted by the architects and builders whose commitment and enthusiasm for the project is obvious.”
Mr Russell said: “After a site visit yesterday, I was left with no doubt that this is an amazing, exciting project with so much vision, which will take the Octagon forward - hopefully for another 50 years!
“I cannot wait to see the final outcome of this very ambitious scheme and wish all involved every success.”
Roddy Gauld, Chief Executive at the Octagon Theatre, said:
“The Octagon is a remarkable story of a college lecturer and five students who designed a revolutionary new theatre.
“That theatre became the Octagon, and now over fifty years on, it’s an absolute honour to show Gerry and Phil, two of those students, around the site.
“The theatre they imagined was flexible, innovative and had community at its heart. This redevelopment will continue those principles including creating more space for our youth and community work.”
The Octagon has been a jewel in Bolton’s crown for more than half a century.
Cllr Thomas, who is also the Greater Manchester Portfolio Lead for Culture, said:
“The Octagon has been a jewel in Bolton’s crown for more than half a century and it was great to see the founders’ enthusiasm for the plans and reminisce about the theatre.
“We have supported the Octagon every step of the way from its conception and it is exciting to see the work being carried out to transform the theatre for its next chapter.
“It is a crucial part of the town’s culture and heritage and we can’t wait to see it open its doors to the community once again.”
The new town centre building is set to reopen in 2020.