Which varietal is permitted for Grosses-Gewächs wines in Nahe?

Grosses Gewächs (GG) wines are a classification in German wine law that signifies high-quality dry wines from specific vineyards. In the Nahe region, the only varietal permitted for Grosses Gewächs wines is Riesling. This is because Riesling is recognized for its ability to express the terroir and has a long-standing tradition in Germany, particularly in regions like Nahe. The strict regulations surrounding Grosses Gewächs wines require that they be made from grapes grown in designated grand cru sites, and Riesling is the grape variety that exemplifies this category in many German wine regions.

The focus on Riesling for Grosses Gewächs highlights the important characteristics of the grape, such as its acidity, fruitiness, and ability to pair with a variety of foods, all of these factors contributing to the wine's overall quality and profile. Thus, the answer indicating that only Riesling is permitted is rooted in the specific criteria that govern the production of Grosses Gewächs wines in Nahe.