Nowhere is the old adage that vineyards are symbiotic with rivers better evidenced than in Germany. All its major wine-producing areas are in close proximity to rivers. In a land so far north, as far as the vine is concerned, the mitigating effect of a river on frosty air can make the difference between success and failure for the crop. In cuspal areas, like the Saar and Ruwer, the rivers are of critical importance.

It's possible to delineate four major wine-making areas; the Mosel to the west, the central Rhine, the eastern wines of Wurttemburg and the southern wines of Baden, or the Upper Rhine. This division is slightly arbitrary as the Mosel joins the Middle Rhine at Koblenz, but in broad geographic sweeps it's accurate. The westerly Mosel is properly called Mosel-Saar-Ruwer, as the upper reaches of the Mosel near Luxembourg contain the two eponymous valleys. In the Saar and Ruwer the vintages are successful in roughly only four years out of ten, but when it works it works well, and they can produce some of Germany's most sublime wines.

The middle Mosel is home to the ubiquitous Piesporter as well as some very fine wines. At this point the river has cut through slate, and its sides can be as high as 700 feet. These precipitous slopes along the deeply meandering Mosel are where the vineyards are, mostly producing Riesling grapes. Bernkastel shares a similar topography, but here it reaches its apotheosis. North of the bridge at Bernkastel is a wall of vines, 700 feet high and five miles long - a sight unmatched except perhaps for stretches of Portugal's Douro. Between the Mosel and the Rhine is the Nahe, and its wine bears some of the characteristics of both of those areas. It has the clean, grapey flavours of a good Mosel, as well as the intensity of the fuller Rhine wines.

The central area contains Germany's best known regions - the Rheinpfaltz, the Rheinhessen and the Rheingau, and is home to many of Germany's finest wines. The Pfaltz, or the Palatinate, begins north of Alsace on the French border. It's the driest and sunniest part of Germany and produces big quantities of commercial wines. The most famous names of the Rheingau are Schloss Johannisberger and Schloss Vollrads, both of which are elegant and prestigious. The Rheinhessen lies in a bend of the river, with the Nahe to the west and the Palatinate to the south. Most of its wines are unexceptional; wines like Niersteiner and Liebfraumilch form the bulk of its produce. The most common grape here is the Muller-Thurgau, followed by the Sylvaner.

Surprisingly the southern and eastern area of Baden-Wurttemburg produces less wine than the north and its production is spread across a hundred mile stretch on the western edge of the Black Forest. Unremarkable reds are made here from the Trollinger grape, which rarely match the whites in quality. Wines from Baden come in a distinctive flattened bottle called a 'stein'.

Wine of the Week

Guldentaler Schlosskapelle Riesling Spatlese 1997

This is a late-picked (Spatlese) wine from the Nahe. Like many of the flowery-scented wines from here, it's at it best without food. Light and fruity with a faintly acidic aftertaste, its natural sugars have produced 9% alcohol by volume. Remarkable for under a fiver in old money.

Available Superquinn, RRP €6.29