It was the first time the public had been invited to see the Japanese-themed mural, created in 1892, since it was discovered beneath hardboard lining in April during demolition work.
Ella Van Zijl described it as "amazing".
"It's so spectacular. I think it should definitely be preserved and maybe displayed in the Otago Settlers Museum," she said.
Monica and Tim Wren were also impressed by the scale and beauty of the piece and said as much as possible should be preserved somewhere the public would get to see it.
Architectural conservator Guy Williams said those at the open day were "excited and very thrilled to see it".
"The response from the public was quite incredible," he said.
Along with expressions of amazement and pride in the find, the message "heard loud and clear" was that the public wanted it preserved.
The Dunedin City Council, Historic Places Trust, Dunedin Public Art Gallery and Otago Settlers Museum are still deciding on the future of the mural, with a meeting scheduled tomorrow to discuss Mr Williams' research.
A decision would then need to be made about retaining and conserving it, he said.
"I'd be very surprised if something of it does not go into the Settlers Museum, in at least the interim, and end up in the Port Chalmers museum."
