Neighbouring farmer Chris Mulholland said windows in the Serpentine Diggings church were smashed, a coal range wrenched apart and a fire extinguisher stolen, which was later recovered on the roadside.
A shot was fired through a nearby musterers’ hut window and gates apparently rammed with a 4WD vehicle.
It was disappointing and dangerous, Mr Mulholland said.
"You wonder what’s going through their minds."
As well as damage to the historic building, the vandals risked creating huge problems for the properties in the area, he said.
"Ripping strainers out and they ram three or four gates and there's a lot of mustering to do if everybody's stock is all mixed up, and those sorts of things as well.
"It’s another consequence, it's not getting away from the vandalism of the [buildings] but there's lots of other consequences of what they're doing."
Remains of a fire had been found despite the area being in a restricted fire season.
"You put a sign up on a gate and say, ‘no hunting’, or whatever, and they start shooting it.
"Well, they don't know 500m on the other side of the gate that there's a person on a pushbike.
"So it's quite dangerous if you shoot a sign, they're not looking half a kilometre behind the sign, but they're still shooting at it."
The whole episode was upsetting, he said.
Department of Conservation Central Otago operations manager Charlie Sklenar said a team was at the site yesterday assessing the damage and taking stock of what was needed for repairs.
Making the building watertight to prevent further damage was the first priority, Mr Sklenar said.
"Vandalism of any type is always disappointing, but when it’s on our iconic heritage sites it’s devastating.
"We can repair, patch up and replace things, but once you start introducing modern materials, they’re not the same.
A Heritage New Zealand spokeswoman said the agency was unaware of the damage until contacted by the Otago Daily Times.
The agency had contacted the Department of Conservation as it was the landowner, she said.
"We would expect to work with the landowner and any other stakeholders to assess the extent of the damage, consider appropriate solutions, and determine any conservation and archaeological requirements needed to support the protection of this important heritage place."
The Serpentine Diggings, on the Rough Ridge Range, was one of the most isolated goldfields and townships in Otago.
Home to about 500 miners, the settlement had included two-storey hotels, a church, cemetery and racecourse, as well as scattered residences. The church was one of the few buildings still standing.
A police spokesman said police were first notified of the damage on February 16.
Inquiries were ongoing, he said.
