Throughout the Loire Valley, there is an estimated 1000km of subterranean tunnels used for everything from houses to restaurants.
Just as the soils, or terroir, of the region aids production of some of the world's finest grapes and wines, so do the caves - as giant wine cellars. The humidity of the caves helps keep the corks moist and the constant chilly temperature - about 12C year round - keeps the bottles cool.
One such cellar tunnel system can be found at Caves Duhard in Amboise, a town 15km east of Tours. The cellar, in what are known as "troglodyte" caves, was cut into the sedimentary rock walls on the banks of the Loire River.
The stone, known as tuffeau, is so porous it is only about 20 per cent heavier than water. The tunnels were created in the 16th century and it is thought that stone from them was used to build the nearby Chateau Royale.
Caves Duhard winemaker Daniel Gatay says the caves house bottles going back to 1874 "but my objective is to create a pleasurable experience, whether it is an old or new wine".
As our tour group delves further into the tunnel system, collections of labelless bottles are stacked on either side of us.
"There is no point in putting labels on them," Gatay says. "The humidity turns the labels black and they fall off.
"It's best just to keep track of the vintages in piles and make a note of what year is where."
He stops in front of a small collection of about eight to 10 dusty bottles that look no different to the others. "The 47," he says. "An extraordinary vintage."
Caves Duhard produces several varietals, including chinon, bourgueil and montlouis, but is best known for vouvray - made from chenin blanc. Vouvrays from good vintages can age far longer than most New Zealand whites with some over 100 years old still drinking well. Want a chenin blanc from 1874? It's yours for a bit over $3000.
None of us is keen to spend that much on a bottle but most decide to buy a bottle from our birth years. Luckily, most are in their thirties so the cost isn't too pricey (about $60) and Gatay labels and signs our bottles.
He then explains that away from the cool dark of the cave, vouvray wines will age a lot faster, so they should be drunk within the next two years.
"So, how will you store them?" he asks as we are leaving. "Do you have a cave?"
A cave? No, none of the group has their own cave.
"No cave? Oh, well, best put it in a paper bag and keep it in the warmest part of your refrigerator."
Mine is inside a couple of brown bags in my fridge's vegetable compartment, waiting for a special occasion.
Getting there: Low-cost airline AirAsia now flies from Christchurch to Paris, via Kuala Lumpur, and premium economy passengers can enjoy lie-flat beds.
Amboise is a 15-minute drive from the city of Tours which is an 80-minute train ride to Paris.
Further information: To find out about tour packages for the Loire Valley and other regions of France, see tempoholidays.co.nz. Tempo Holidays is a division of Cox and Kings.
PK Stowers travelled to the Loire Valley with assistance from Tempo Holidays and Air Asia.