Cachoeira de Emas sits on both banks of the Mogi Guaçu, and it is one of the most important freshwater fish breeding grounds in Brazil. During the piracema — the seasonal spawning migration — dourado, mandi, curimbatá and piapara push upriver against the current, and fishing is closed to let them through. Human engineering has had to accommodate them. A fish ladder built here stood almost five metres high from 1942 to 1966, was remodelled in 1984, and now works at three metres, carrying commercial species toward the headwaters. The falls also drive a small hydroelectric plant that supplies power to the city. The rest of the year the district is a fishing and boating destination, with houses to rent near the water and restaurants serving the dourado that comes out of it.

In 1971 the Academia da Força Aérea moved from Campo dos Afonsos in Rio de Janeiro to a purpose-built campus on the edge of Pirassununga, bringing with it a bronze bust of a former commander, Colonel Fontenelle, whose name went onto the new airfield. Every current and future officer of the Brazilian Air Force trains at Campo Fontenelle. It is a strange and wonderful thing for a town of 77,000 to host — a constant overhead soundtrack of training aircraft in the circuit. The base is also home to the Esquadrilha da Fumaça, the Smoke Squadron, created on 14 May 1952 and now flying Embraer A-29 Super Tucanos in gloss blue. The team was disbanded in 1977 and brought back in 1983, and it still occasionally puts on displays over its own field for the public.

The air force is not the only uniform in town. Pirassununga also holds Fort Anhaguera, which once housed the 13th Mechanized Cavalry Regiment of the Brazilian Army. The concentration is unusual: a mid-sized interior municipality carrying both an army post and the national academy of an entire air force. Geography explains part of it. This is high, open, well-watered country at 627 metres, within reach of São Paulo and Campinas but far enough from either to have room — the kind of ground military planners like for training establishments that need airspace, manoeuvre area and quiet.

Three sugarcane distilleries operate in Pirassununga: Cachaça Sapucaia, Pirassununga Cachaça, and the one that made the name national, Pirassununga 51. It was founded in 1959, a year after Brazil won its first World Cup, and by the 1970s it had become a household brand on the strength of a slogan that entered everyday speech — "51, uma boa ideia," a good idea. Export markets came only in the 1990s. Cachaça is distilled from fresh sugarcane juice rather than molasses, which is what separates it from rum, and it is the spirit at the base of the caipirinha. A great deal of Brazil's national cocktail begins in this one municipality.

The town's third identity is research. The University of São Paulo runs its Faculdade de Zootecnia e Engenharia de Alimentos here — the College of Animal Science and Food Engineering — which puts a serious agricultural and food-science faculty in the middle of cattle and cane country. Pirassununga is also the seat of CEPTA, the national research and conservation centre for continental aquatic biodiversity, linked to the Chico Mendes Institute in Brasília. That posting is not accidental either. A centre devoted to Brazil's freshwater life belongs at a river that has been famous for its fish since before Portuguese was spoken here, in a town named for the sound they make.