Australia is a vast country, its wine regions stretching over 4,000km from Margaret River south of Perth in Western Australia to Hunter Valley north of Sydney in New South Wales. Those regions vary so much, in soils, in grape varieties grown, and, more than I realised, in climate. Despite those differences, there is a huge level of support for and interest in other regions, even when they're hundreds of kilometres apart.

The one exception to this comradeship is Hunter Valley. Two Australian girls we met in Argentina informed us the wine was terrible. When we told people in South Australia that our Australian journey would culminate in Hunter Valley, the reaction was an incredulous yet muted, "Oh." In Victoria the reaction was more impassioned: "You're saving the worst to last!"

At first I didn't understand their dislike, dismissing it as simple jealousy. Hunter Valley is near Sydney, and its wine industry revolves around Australia's biggest city which is so far away from Australia's other wine regions. So I decided to ignore all those reservations, not least because I wanted to taste and discover more about the unique wine of Hunter Valley: Semillon.

We drove eight hours from Rutherglen through endless nothingness, bypassing the capital Canberra and Sydney (which we returned to). I expected Hunter Valley to be like Napa Valley: close to a major city, beautiful, and full of decorous tasting rooms and expensive restaurants. Instead, it's rather ugly, a flat valley with a small, truncated mountain range to the west, and its tasting rooms looked like they hadn't been touched since the 1970s. There were few restaurants, the locals were unfriendly, and it baffled me why people from Sydney - residents and tourists alike - visit the region so much. In short, all those negative opinions others had voiced were right.

Its climate is hot, humid, and windy. Those winds aren't refreshing, but blow the heat and humidity into one's face. The cloud cover smothers the heat further. Hunter Valley really isn't a region made for wine production, yet wine has been made here for two hundred years. James Busby, one of the founding fathers of Australian wine, settled here in the 1820s and the region's proximity to Sydney has sustained its wine industry. I can't imagine a region I'd less want to make wine in.

semillon

For all of Hunter Valley's unsuitability for growing grapes, it produces a unique style of wine. Hunter Valley Semillon is one of the world's most ageworthy white wines, and I wanted to learn more about what makes the wine so individual. The answer is a paradox: the high acidity, low alcohol wines are a result of the warm climate. The grapes ripen quickly in the heat and are picked early (in part to avoid the heavy rain and hail that falls before the end of the growing season). In the heat, the grapes have developed enough fruit flavour to give the wine body and structure but picking early ensures high acidity and low sugar levels. Once the wine is made, very little happens: it's aged for a couple of months in stainless steel before bottling. Young Hunter Valley Semillon is neutral and quite dull, with at best vaguely fruity, herbaceous aromas. As the wine ages, it changes into something much more interesting: waxy, nutty, and honeyed, rich but retaining the high acidity. Wineries delay releasing their best wines for at least five years, and Hunter Valley Semillon isn't worth drinking before then. This makes it one of the few white wines that genuinely improves with age. Try Brokenwood's ILR Reserve 2009 (A$75; $58 ✪✪✪✪✪) for a great example of how Semillon ages - this wine still feels remarkably young, with fresh acidity and grassy aromas, but nutty aromas are beginning to develop and there's a steely, mineral, waxy texture. Such wines are best enjoyed with food, especially with the Asian cuisine so popular throughout Australia.

shiraz

The other grape variety Hunter Valley is known for is Shiraz. Again paradoxically, the heat produces a restrained style, quite different from the wines of South Australia. The quick ripening and heavy autumn rains lead to an early picking, which means that the Shiraz wines aren't as rich and fruity. Their restraint made them seem quite dull in comparison, though there is an earthy texture which has led to comparisons to the northern Rhône - I felt the wines lack the depth and complexity to justify those comparisons.

Grape growing is so tricky in Hunter Valley that wineries source grapes from elsewhere, even from as far afield as Margaret River. It says a lot about Hunter Valley that the one wine we bought while there was a Shiraz from the cooler climate of Canberra ...