Christchurch City Council has just over two weeks to decide whether to retain all of the Town Hall's heritage features or to redesign some parts to be more functional.
The council decided last year to fully repair the facility and the Government recently gave it control of that work.
A total of $158 million is budgeted for the hall's restoration and a new performing arts precinct beside the Isaac Theatre Royal.
All four options include full refurbishment of the main auditoriums, with the only differences being the extent of change to the badly-damaged southern wing.
The most conservative option is to rebuild the wing to its original state, while other options involve replacing it.
Each option is expected to cost about $128 million, which leaves about $30 million for a performing arts precinct.
Project director Liam Nolan said a plan for the precinct is still being developed. He acknowledged funding will be tight and private money may be needed.
Councillors will decide which Town Hall option they prefer on 29 August.