Bustillo did not invent the look out of thin air. He took his cue from the Hotel du Palais at Biarritz, the great seafront resort on France's Atlantic coast, and rendered it at monumental scale: an eclectic composition with the bones of French Neoclassical architecture, clad in brick and quartzite, crowned with slate. The casino and its sibling - the Grand Provincial Hotel, inaugurated in 1950 - were conceived as a single civic gesture facing the sea. Ground broke on 15 July 1938, the spade wielded by Manuel Fresco, the conservative governor of Buenos Aires Province, and the Central Casino opened on 22 December 1939. To dress its interiors, the project brought in the celebrated French designer Jean-Michel Frank, then in Argentina working on the Llao Llao Hotel, alongside the local design house Casa Comte.

Bustillo designed more than the buildings. He shaped the ground between them and the water - the Bristol Esplanade, or Rambla Casino, and the central plaza, laid out between 1938 and 1941. Guillermo Brown Square divides the twin buildings and opens to the sea down wide stone steps, and it is there that Fioravanti's two sea lions keep their watch. The choice of animal is no whim. Sea lion colonies have hauled out on this coast since long before the city existed; Sir Francis Drake noted them when he reconnoitered these shores in the 16th century. Carved in stone at the meeting of esplanade and beach, the lobos marinos turned a local fact of nature into the city's emblem.

This is no boutique gaming room. Inside, the main hall overlooks the Atlantic, and beyond it spread salons for high rollers - some 140 tables of blackjack, baccarat, craps and roulette - and a sea of 630 slot machines. Through the summer season the casino draws around 12,000 players an evening, swelling toward 18,000 on January weekends, when half of Buenos Aires seems to decamp to the coast. The grand canopied entrance once opened onto Patricio Peralta Ramos Avenue, named for the city's founder, but a 2007 refurbishment turned the building to face the seashore esplanade, as if acknowledging where its real front door had always been.

The north building is a small city in itself. Sharing the structure with the casino are a 66-room four-star hotel, the Auditorium Theatre, the Astor Piazzolla Room - named for the tango revolutionary born in this city - and a sports arena that hosted gymnastics and other events at the 1995 Pan American Games, plus a School of Hospitality and a parade of ground-floor storefronts under a beachfront portico. The casino is also one of the marquee venues of the Mar del Plata International Film Festival each November, when the Auditorium fills with directors and stars rather than card players. The twin across the square had its own second act: shuttered for a decade, the Grand Provincial Hotel was reopened in February 2009 by the Madrid-based group NH Hotels. Nearly seventy years after Bustillo drew them, his twin landmarks still anchor the rambla, still face the same gray-green Atlantic, still wearing their slate roofs against the wind. They are not just buildings on Mar del Plata's coast; for most Argentines, they are the image the word 'coast' calls to mind.