Thousands of people will get a behind-the-scenes look at the Australian War Memorial's collection of military equipment, including tanks and rockets.
Five-thousand people will attend the sold-out "big things in store" event at the memorial's storage facility in Canberra on Saturday.
Members of the public will have the chance to see new acquisitions and popular objects from the national collection not on display.
Australian War Memorial Director Matt Anderson said there were currently more than 121,000 items in store, with the open day an opportunity to give the public a much greater appreciation of the full collection.
"This is a first glimpse of some of the items yet to be added to new gallery displays," he said.
"This will be a chance to see new acquisitions such as the Saracen Sikorsky S-70, the Memorial's first Black Hawk Army helicopter which performed 30 years of service including peacekeeping and humanitarian operations.
"Favourites include the much-loved G for George Avro Lancaster Mk I Bomber alongside some of the memorial's more recent acquisitions, such as the F/A-18 Classic Hornet."
The Boeing CH-47 Chinook helicopter, which retired with 16 years of service in April 2016, will also be on display.