Phu Quoc nuoc mam (fish sauce) is among the most prized in Vietnam — the island's UNESCO-recognised traditional production method involves layering anchovies and sea salt in large wooden barrels and leaving them to ferment for a minimum of twelve months. The resulting liquid, tapped off the bottom, has a depth of flavour that factory-produced fish sauce can't match.
Several factories in and around Duong Dong welcome visitors. The smell is extraordinary — not unpleasant once you adjust, but unmistakeable. The Hung Thanh factory on Tran Hung Dao Street is one of the most accessible for self-guided visits. The bottled product makes an excellent and genuinely useful souvenir. Free to visit.