The shared avenue is the most extraordinary thing about Chuy, and the most ordinary to the people who live there. The central boulevard carries different names depending on which curb you stand on - Avenida Brasil on the Uruguayan side, Avenida Uruguai on the Brazilian side - with the frontier running down the planted median between the traffic lanes. There is no wall, no obvious barrier. Pedestrians drift across as casually as crossing any street. The two municipalities even share their culture deliberately, staging a joint carnival billed as "Chuy-Chuí Without Borders." Residents speak Spanish and a local Uruguayan Portuguese, switching tongues mid-conversation the way they switch sidewalks. It is a place where nationality is something you wear lightly, because the line is right there and crossing it costs nothing.

Chuy lives on the boundary it straddles. The Uruguayan side filled with duty-free shops and a casino; the Brazilian side lined up with supermarkets and stores selling clothes, shoes, and household goods. The price difference is the whole point. It is not unusual for Uruguayans to drive 340 kilometres from the Montevideo area just to shop here, loading up on goods that would cost far more at home. That two-way bargain hunting became the engine of the local economy for both towns. The 2011 census counted 9,675 people on the Uruguayan side, but the daily population swells with shoppers and traders crossing back and forth. Among the residents is a small but significant Palestinian Uruguayan community, mostly Muslim - one of many threads in a town that has always been a meeting point.

The boundary that defines Chuy was fought over long before it became a shopping district. In 1751, the governor of Montevideo ordered military posts built on both banks of the Chuy stream, as Spain and Portugal argued in distant courts over who owned this contested frontier. Soldiers held the line; treaties redrew it; armies marched across it. The name itself reaches back further, most scholars tracing "Chuy" to the Tupi-Guarani language - by one account the name of a yellow-breasted marsh bird, by another a phrase meaning "river of brown water." For a century and more, Uruguay and Brazil kept amending their shared boundary, planting markers through the twentieth century to settle exactly where one country ended and the other began. The casual avenue of today rests on generations of careful, contested cartography.

Beyond the busy avenue, the land opens to a quieter Atlantic edge. About ten kilometres away, near the Barra del Chuy inlet, a lighthouse marks the coast, and the beaches here stay relatively free of crowds. Sea lions haul out along this stretch of shore, and the surrounding marshland teems with the wildlife of the Rocha wetlands - capybaras, water birds, and the dense, low forests that fringe the lagoons. This corner of Uruguay is the country's far eastern frontier in every sense: the last town before Brazil, the edge of the continent's southern coast, and a landscape where the human bustle of the border gives way quickly to wide skies, salt air, and the long Atlantic horizon.