The village has become very good at packaging tourism, just as it has successfully injected the "pile 'em high" ingredient into its glorious wine-making tradition. Too successfully, some argue - none louder than two Britons who have taken on the German establishment in a crusade against the modern-day barbarism that has allowed outstanding vintages to submerge in an ocean of sweet-and-sour Liebfraumilch.
Authors Stuart Pigott and Hugh Johnson have fired missives accusing the industry of destroying the reputation of its products by its endeavour to maximise profits. But the real culprit, in their view, is the very culture of wine-making, and the legal framework that is supposed to guarantee quality. Putting it bluntly, as Mr Pigott often does when trashing one vintage after another, "the 1971 Wine Law is an ass... It is a form of masochism that is defrauding the public."
In 1971 Germany rationalised its system of classification, abolishing a complex hierarchy that was similar to that of France. The result is that too many wines can gain the top accolade, but there is nothing on the label to distinguish exceptional vintages along the lines of France's "grand cru" and "premier cru" designations. Worse, the new law amalgamated neighbouring districts into regions, allowing a less well-endowed village to trade on the reputation of another area to which nature has been kinder. "You have a situation where people in one town are legally entitled to exploit people in another town," Mr Pigott says.
And exploit they do. Most producers , however, seem content with the level playing field. The establishment defends the system's democratic credentials and denounces the two Britons as "elitists". While German wine exports and domestic consumption are down, the industry as a whole has stayed solvent by working with narrower margins on a bigger scale of production..
That is precisely the problem, retorts Mr Pigott, a wine critic and painter who has been likened by one prominent insider to a "wild boar charging through the German wine industry". In their book, The Wine Atlas of Germany, Messrs Pigott and Johnson tried to turn the clock back by reviving the old boundaries between districts of wine and plonk, eliciting howls of protests from the latter.
But they have also made some friends. In an old house on Bernkastel's northern edge, Thomas Loosen spreads out a map dating back to 1868. It shows the Mosel's snaking valley and its villages, shaded in three colours. The darkest areas are the ones that attracted the highest tax a century ago, because they were deemed the best vine-growing districts. He shows where we are: at the bottom of a precipitous cliff covered with vineyards. On the map it is bright red. Across the river we see gentle hills, worthless a century ago but now also sprouting young vine stock. The wines from the other bank, like the Dr Loosen label, trade under Bernkastel's good name.
"The law has certainly not promoted the German wine industry," says Dr Loosen. "It only helped the big producers." Thomas Loosen, who helps his brother Ernst run the estate of 10 hectares, is one of the smaller producers. On a silver tray in the living room lie the family jewels: pieces of rock that have sustained their wealth for generations. There are slabs of grey Mosel slate, and the highly-prized red sandstone which nurtures the best Rieslings.
The estate's young cellarmaster, Bernhard Schug, is unashamedly elitist. "The quality certainly depends on the producer, but also on the location of the vineyard and that you cannot change," he says. Like the two Britons, Mr Schug, a beer-drinker with a degree in animal husbandry, is something of an enfant terrible of the wine world, positively boasting of his low yields that ensure a more concentrated nectar. The quantities are indeed pathetic, but the two 1995 vintages he serves up after a painfully long search for a corkscrew are exquisite. "We are at the beginning of a renaissance for the Mosel wine," he declares. "I hope the times when people added anti-freeze are over..."
Because the Loosen estate has established a reputation for excellence, it is able to make up for loss of volume by charging higher prices. There are many other great wines waiting to be discovered, but under the present system such treasures will remain hidden. "Germans have a lot of problems with national pride," Mr Pigott says. Until that changes, keep opening those bottles of syrup and vinegar marked Qualitatswein and brace yourself for the occasional happy surprise.