What local dishes should I try in Vietnam, and where should I look for them?

That registration is the single most useful fact about Vietnamese food for a visitor, because nuoc mam underlies most of what you will eat and because the PDO makes Phu Quoc a place you can taste rather than a brand you can read. The island sits in the Gulf of Thailand off the southwest coast, and the designation ties the name to that origin in EU law — which is why bottles elsewhere carry careful wording about where the anchovies were fermented.

Beyond that, regional difference does the work. The central coast is the part of the country most travelers under-eat. Hué was Vietnam's imperial capital, and the Complex of Hué Monuments covers the walled palace city that gave the region a court cuisine distinct from the north and south — small, numerous, carefully composed dishes, and the chili-and-lemongrass beef noodle soup bún bò Huế that carries the city's name. Down the coast at Hoi An, cao lầu is specific to the town rather than to central Vietnam at large.

Go inland and the produce changes. The Da Lat highlands grow temperate vegetables, strawberries and coffee at altitude that the delta cannot, and the Mekong Delta around Can Tho runs on freshwater fish, river snails and fruit rather than sea catch. These are not variations on one national menu; they are different larders.

On Phu Quoc the fish sauce is made in barrel houses where wooden vats stand two stories high, and the smell reaches the road well before the building does. In the highlands around Da Lat the morning markets open in genuine cool, with vegetables that would wilt in the delta stacked under cloud that does not lift until mid-morning.

The geographical indication is the reason to buy fish sauce where it is made rather than at an airport. A PDO protects a name tied to a place and a method, not a recipe — so the premium on a Phu Quoc bottle reflects a registered origin claim that can be enforced in EU markets. Buying it on the island means buying inside the designated area, which is as close to the product as a visitor can get.

• Central coast — Give Hué and Hoi An separate meals rather than treating central Vietnam as one cuisine; the dishes are town-specific.
• Highlands — Eat vegetables and drink coffee in Da Lat, where the altitude makes both possible.
• Delta and island — Finish on freshwater fish around Can Tho and fish sauce on Phu Quoc, where the PDO originates.

Getting to the food means moving through a long country, and Phu Quoc in particular is an island reached by air or ferry rather than a stop on an overland route. US citizens need a visa for the Vietnamese mainland obtained before travel, with the island the sole exception for stays of 30 days or less — so a food trip that treats Phu Quoc as a bolt-on has a paperwork consequence. The EU designation dates from 2012 and governs the name in European markets rather than regulating what is sold locally.

The places question in this chapter covers Hué's imperial complex and the rest of Vietnam's World Heritage list, and the when-to-visit question explains the regional climate split that determines when each of these regions is pleasant to eat in.