It was 1998 and wine lover John Geber was on holiday enjoying a casual cycle through the Barossa when he saw a grand old building for sale that happened to have a phone number in the window.

He rang and bought it ... basically, just like that. As you do.

The bluestone structure was the derelict Chateau Tanunda winery, probably the most historic building in Australian wine.

In fact, for years it was the largest winery building in the Southern Hemisphere, full stop.

"It was intact on the outside, but that's where it ended ... it was pretty dilapidated," John's daughter Michelle, now Chateau Tanunda's managing director, said.

So much so it has taken the best part of 20 years and millions of dollars to replace the roof and the roosting pigeons and, bit by bit, bring the magnificent building back to its glorious best.

But it was a labour of love for John who made his money from wine, exporting to Europe and Asia with his Kangaroo Ridge label.

These days the 37,674-square-foot chateau is a world class winemaking facility, with more than 350 acres of vines, a croquet lawn, a cricket oval, and hospitality spaces that attract more than 100,000 visitors annually.

"We've restored the building and the brand itself, but there are still things we want to do," Michelle said.

"We pour a lot of that back into the business, including the winery and cellar door.

"Next up we want to build a viewing platform so people can take in the vineyards and valley views ... there's always something else."

Such is the grandeur of the building and its history - for years Australia exported much of its wine to Europe from there, especially after the French wine industry had been ravaged by phylloxera - that it is still allowed to retain the now-protected word "chateau" in its name.

That's some achievement because the French are mighty protective of their naming rights.

"We fought to keep it a chateau obviously," Michelle said.

"We feel this is a chateau in every sense of the word: 100 metres long, a 20-metre tower, built into a hill so the temperatures were controlled pre-airconditioning, a rich history ..."

Having said that the test of a winery is the quality of the wines. And with huge export markets in the US, Europe and Asia, and burgeoning sales in Australia, Chateau Tanunda is clearly doing something right.

"We proudly do Barossa wines - rich, bold, full of flavour, but with a certain elegance, that's our house style," Michelle said.

"Our flagship is the Everest range, that's the pinnacle. But our Old Vines Expressions range is exciting. These are rare, collectible wines in much smaller volumes.

"So, for the first time we're about to release a 150-year-old vines shiraz. It will sit alongside 15 vintages of 100-year-old shiraz. We have 100-year-old vine semillon as well.

"These are some of the oldest vines from around the world, and they're ours. It's exciting."