Which of the following regions is known for producing premium Riesling?

Eden Valley is recognized for producing premium Riesling due to its ideal climatic conditions and unique terroir. This region, which is part of South Australia, has a cool climate that aids in the slow ripening of Riesling grapes, allowing for the development of complex flavors and high acidity. The altitude of Eden Valley also contributes to a significant diurnal temperature variation, which further enhances the acidity and aromatic profile, making it particularly suitable for crafting high-quality Rieslings that can express both fruitiness and minerality.

The other regions mentioned may produce other types of wines, but they are not primarily known for their Riesling. Marlborough, for instance, is more famous for its Sauvignon Blanc, while Barossa Valley is known for robust Shiraz. Martinborough has gained recognition for Pinot Noir but does not have the same reputation for Riesling as Eden Valley.