The planned state government office at the Civic Hall site will cost up to $100 million to build through a private-public partnership.
Ballarat City Council unveiled plans for a $6.3 million internal refurbishment of the main hall on Friday, however the lower hall was not included.
State government plans released in April showed the new GovHub would occupy the lower hall site.
Ballarat mayor Samantha McIntosh said architects would be able to maintain the lower hall and integrate it with the planned government offices.
“A clever architect can do all those things well because the GovHub project does sit at the lower hall site,” she said.
“There is a $47 million commitment by the state government that looks at moving jobs, and also $100 million for the build.
“The state government has made a huge commitment.”
The mammoth project to make the site once again available for public use will include a 1300-seat-capacity main hall.
Three hundred seats will be refurbished for the upper level dress circle.
A retractable wall allowing the area to be separated from the main hall will also be added.
The stage will also have a retractable wall to allow for a 100 seat theatre facing a secondary, smaller stage, which will be able to show movies or smaller shows.
Work will also be done to modernise the building’s acoustics with new wall and roof panels, while a cafe is planned for the ground floor.
There was no plan revealed for the derelict lower hall site.
State government plans to add 1000 jobs to the Civic Hall precinct have included replacing the lower hall and building new offices next to the main hall.
It is expected the project will be finished in late 2018.
Work is already well underway on the area outside the hall and is expected to be finished early next year.
The facade of the hall was also refurbished.
Cr McIntosh said the internal plans would maintain the cultural and social history of the building.
“It is using as much that we possibly can of what is already there,” she said.