The hugely-popular, but very isolated, tourist attraction has had fire bearing down on it from all sides and all activities, tours and accommodation are currently suspended.

The Ruined Castle bushfire (17,058 hectares) has joined with the massive Green Wattle Creek fire (262,729 hectares) and much of the Jenolan Caves precinct is under threat.

READ MORE: Third State of Emergency declared this bushfire season

Fire and Rescue NSW Zone Commander Superintendent Brett Jackson said teams of firefighters had been on scene since Boxing Day.

"The main focus for us is Caves House, that's the main thing we want to protect, but there's a lot of other historic buildings there," he said.

"We've had spot fires around Caves House."

A vacant house has been destroyed in the blaze, but crews fear more buildings have been lost.

Supt Jackson said because the area is so volatile right now with active fire still burning, it was hard to assess the full extent of the damage.

"We think we might have lost a few buildings, but the roads are closed and we still can't get though," he said.

READ MORE: Australia's catastrophic bushfire season

"Nothing that we believe was historical has been lost."

Supt Jackson said while the fire had already burnt through some areas, many of the roads were too dangerous to use due to burnt-out trees falling down onto roads.

"Every 10 minutes we're hearing a big tree crash and land," he said.

Supt Jackson said ahead of dangerous fire conditions predicted on Saturday, firefighters had contained the fire on three sides of Caves House.

"There's a very active fire coming towards this way, but it will have to come down quite a steep slope," he said.

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"We've hoping we'll have full containment in the next couple of days, but we are worried about the nasty weather coming up on Saturday."

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