The name is a relic of a more glamorous era. Cassino means casino, and the beach earned it honestly. When the resort opened in 1890, developed by a company that built a tourist complex on the dunes and debuted it on the 26th of January that year, it drew well-off Brazilians, many of European descent, to gamble in luxury hotels overlooking the Atlantic. They played poker, craps, and blackjack while the surf rolled in below. The good times did not last. The persecution of Italian and German communities during the Second World War, followed by Brazil's nationwide ban on gambling in 1946, gutted the resort's economy and shuttered its gaming tables. The casinos vanished. Only the name, and the faded grandeur, remained.

Cassino's flat immensity has attracted some unlikely visitors. On 12 November 1966, as a total solar eclipse darkened the sky above the beach, NASA scientists and the U.S. Army stood on this sand and fired sounding rockets into the upper atmosphere to study it in the eclipse's shadow. A decade later the beach claimed a permanent resident: the ship Altair, driven aground by a fierce storm in June 1976, has rusted on the sand ever since, sixteen kilometers from Cassino's center, a hulk slowly surrendered to salt and tide. Nearer the town stands a cement statue of Iemanjá, the ocean goddess of Afro-Brazilian faith, sculpted by the local artist Erico Gobbi and facing out toward the water she is said to rule.

Where the beach meets the port, the great breakwaters reach out into the Atlantic, walls of stone built to keep the navigation channel to Rio Grande open. Along the western jetty, the Molhe Oeste, you can ride something delightfully odd: a small cart pushed by sail, gliding along tracks for roughly four kilometers out toward a lighthouse, a journey of about twenty minutes with dolphins sometimes surfacing alongside. The waters here teem with marine life. Cassino is celebrated for hosting an enormous gathering of sea lions, drawn to the rich southern Atlantic, and visitors take to boats to watch the animals haul out and bask, a wild counterpoint to the beach's faded resort past.

Everything about Cassino runs to excess, even its sports. The beach hosts the Cassino Ultra Race, billed as the largest beach ultramarathon in the world, sending runners pounding 230 kilometers across the sand, beginning down near the Chuí frontier and finishing at Cassino itself, with shorter punishing distances of 135 and 73 kilometers for those who prefer mercy. Around 150,000 visitors come each year, peaking in the southern summer between December and January, to swim, surf, and simply stand on a shore that seems to have no end. In 1994, Guinness World Records made it semi-official, recognizing Praia do Cassino as the world's longest beach, a title forever shadowed by the paradox that makes any such measurement impossible to truly settle.