Which of the following regions is known for producing Riesling?

The region known for producing Riesling is Alsace. Alsace is located in northeastern France and has a climate that is particularly well-suited for growing this aromatic white grape. The region benefits from a rain shadow effect created by the Vosges mountains, which helps to ensure dry conditions favorable for grape cultivation. Riesling from Alsace is renowned for its purity of fruit flavors, minerality, and aromatic profile, which can vary from dry to sweet styles. The region's unique terroir and tradition in winemaking contribute to the distinctive character of its Riesling wines.

Bordeaux is primarily associated with the production of red and white blends, focusing on varieties like Cabernet Sauvignon and Merlot, rather than Riesling. Napa Valley is known for its high-quality wines, including Cabernet Sauvignon and Chardonnay, but it does not have a reputation for Riesling. Rioja, primarily known for its red wines made from Tempranillo, also does not focus on Riesling production. Thus, Alsace stands out as the definitive region recognized for its Riesling wines.