Whanganui Regional Museum will be closed for more than a year for seismic upgrading, which is due to start in January.
In an update, the Whanganui District Council's deputy property manager Leighton Toy said the museum was the third public building to undergo earthquake strengthening, after the Opera House and Alexander Library.
But, Mr Toy said, although strengthening the building was expected to take four to six months, it would take longer than that to recreate the "museum experience" once the seismic work was finished.
Councillor Hamish McDouall expressed concern about the timing of the closure. He said it would be preferable if the museum was closed during the low tourist season rather than across two high tourist seasons.
But Mr Toy said there was a health and safety component involved as well, and that was why it was easier to close and operate from temporary headquarters in Ridgway St in the old central Post Office building.