Dunedin Chinese Garden manager Margo Reid said security systems indicated the pair, a male and a female, entered the garden over the wall at 4.30am.
Their visit to the gardens was recorded in its entirety on security cameras, which showed them spending some time walking around the gardens, then trying, with great difficulty, to get back out.
Some penjing (potted landscapes) belonging to the gardens' gardener were destroyed, gardens trampled, and walls and roof tiles damaged where the pair managed to get out.
Footage showed the male boosting the female on to the roof, before then scrambling out himself.
Alarms and sensors in the garden were triggered and a security firm was automatically notified immediately, but by the time security personnel arrived the pair had gone, Ms Reid said.
Police had taken prints from the gardens and were reviewing security film from the garden.
Senior Sergeant Craig Brown said it appeared the pair used a ladder from a nearby construction site to get up the outside wall of the gardens.
Ms Reid said it seemed as though the pair had entered the gardens as a prank, but staff there were "absolutely gutted" about the damage they caused.
"Some of the stuff they have damaged was personally valuable to our staff."
