Research has found that work needs to be done before Christchurch's Cracroft caverns can reopen.

The World War two bunkers are located 30 metres below the suburb of Cashmere.

They were built to be the main defence headquarters for the South Island.

Canterbury University used the caverns for ring-laser experiments from the 90's until the earthquakes six years ago, but have been closed ever since.

Professor of Optical Physics Jon-Paul Wells said he's been in the cavern since the earthquake on geotechnical visits.

"[There is] quite significant rock fall out of an exposed part of the roof, an area where the bomb-proofing was never completed, so there is quite a bit of rock on the ground."

He is optimistic that they can reopen.

"We have had a couple of geotechnical reports and basically they all come back saying the same thing that it's fundamentally sound. There is work required, but it is not an insurmountable problem."

Wells said while they caverns aren't high on the Councils priority list, they are of significant public interest.