On a recent river cruise along the Rhine I admired mile after mile of grape vines growing on the steep banks either side of the river. The rows rose in vertical lines at the sort of angle you would rest a ladder on a wall you intended to paint. The slopes are so steep that workers harvesting grapes sit on trolleys pulled up by ropes.

One day our ship moored at Koblenz, which means ‘confluence’, because it is here the Mosel River joins the Rhine. The Mosel, spelled Moselle in France and Luxembourg, is known for growing some of the world’s best Riesling so I took a trip up the Mosel to the village of Winningen at the centre of the lower Mosel winelands .

Along the Mosel nearest the Rhine the vines grow in horizontal rows, each on a narrow terrace gouged out of steep cliffs in Roman times. It is here say the locals, who maybe are not unbiased, the best of the very best Riesling grows. The area is called Uhlan Terrassen, or owl terraces, and they are some of Germanys steepest vineyards, with slopes at an angle of 65 degrees.

Herbicides and insecticides are not allowed in the vineyards, although fungicides are and when needed these are sprayed by helicopters, and harvesting is by hand

Winningen annually stages Germany's oldest vintage festival, dating from 1551, at the end of August, and the town was birth place and is the final resting place of August Horch who founded the Audi motor company, Audi being a Latin form of Horch.

In Winningen I visited Richard Richter Weingut. Grape vines arch across the streets approaching the winery. We left brilliant sunlight to descend into the cellars for a tasting. Large vats line the walls, each topped by a lit candle giving a soft light. The winery was founded in 1838 and is run today by Thomas and Claus-Martin Richter who tend the vines and make their wines.

They own 20 acres of vineyards growing mostly Riesling with Pinot Blanc, Pinot Noir and Chardonnay. 12% of their production is used for sparkling wines made by the traditional method, and by hand – meaning that bottles are riddled in the old manner rather than by machine.

I tasted two Rieslings:

Richard Richter 2015 Uhlen Terrassen Riesling Trocken. This is from their premium vineyards and was crisp dry with good fruit balance. A mouth-watering wine that I bought and had with dinner on the boat a few days later. 13%abv, RS 5.5g/L, acidity 7.6g/L €16.50

Richard Richter 2015 Terra-V. Terrassen Riesling feinherb. The ‘V’ is short for Vulcan, referring to the volcanic subsoil of this vineyard. This wine, marked as ‘medium-dry’ was noticeably sweeter than the previous, it had an underlying core of acidity–Riesling is a very acidic variety–with tropical fruits and met favour with most in our group but was too sweet for me. 11.5%abv, RS 30.6g/L, acidity 7g/L €16.50

(abv – alcohol by volume, RS – Residual Sugar, g/L, grams per litre)

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Peter F May is the author of Marilyn Merlot and the Naked Grape: Odd Wines from Around the World which features more than 100 wine labels and the stories behind them, and PINOTAGE: Behind the Legends of South Africa’s Own Wine which tells the story behind the Pinotage wine and grape.

Disclosure: Peter May paid for all travel, tours, tastings and wine