Suantang yu — sour fish soup — is the signature dish of Fenghuang and the Xiangxi region. River fish (typically carp or grass carp) are cooked in a broth made with fermented rice wine, fermented vegetables, fresh tomatoes, and dried chilli, producing a soup that is simultaneously sharp, savoury, and slightly sweet. The sourness comes from the fermentation rather than from vinegar, which gives it a more complex flavour than the broth's description suggests. Served with white rice and pickled vegetables on the side.
The dish requires a minimum of two portions to order and costs around ¥40–60 for a meal for two. Every restaurant in the old town offers it; the quality varies significantly. The most reliable versions come from small family-run restaurants away from the main tourist drag, where the fermented stock has had time to develop properly. The dish has become a food identity marker for the region — locals from Xiangxi living elsewhere describe it as the thing they miss most about home.