Canterbury Museum is packing up to prepare for what it is describing as a once-in-a-lifetime redevelopment.
As many as 2.3 million taonga are being moved and stored as building gets underway on the Rolleston Avenue site alongside the Botanic Gardens.
Rising construction costs mean the project budget has increased by $10m in the last year to a total of $205m.
Two years ago museum director Anthony Wight said the redevelopment was needed to protect the museum's historic buildings, its priceless collection, and to bring the interior spaces up to the standards expected of a fit-for-purpose 21st-century museum.
"Some of the buildings have a long list of problems and are either well past the end of their useful life or need major upgrades. They are causing damage to the collections they are meant to protect,'' Wright said.
The buildings leaked and let in insects and because there was minimal air conditioning and no insulation, temperature and humidity could not be controlled.
Today he told Morning Report that once the renovations are finished the museum will be a "world class base-isolated fully air-conditioned facility".
"It's the first time the museum collections will have been in tip-top storage facilities in their life.
"We're moving to a very large secure warehouse complex while the main museum complex is totally redeveloped."
He said visitors can be assured their old favourites will still be displayed.
Three controversial Māori dioramas seem unlikely to be returned though. Wright said the museum was working with Ngāi Tūāhuriri to remove the most offensive parts almost immediately while the rest will be taken away as part of having to empty the museum.
The dioramas have been criticised for their primitive depiction of early Māori life.
Wright said exhibits of a whale and an elephant were among the largest items to be moved.
The museum's colonial street has been among visitors' favourites for many years and it would be carefully dismantled and stored before being reconstructed in the new facility.
"We have heard the public loud and clear - the old favourites like the street, like the whale...they'll all be coming back in the redeveloped museum where there's much more space for exhibits."
Wright promised that some items that have not been displayed for over 100 years would be on show alongside other "wonderful" exhibits that the museum has collected in the last 10 to 15 years but have never seen the light of day.
"It'll be a fantastic new visitor experience full of new treasures as well as the old."