The commission was personal. Williams designed the house as the permanent residence of his father, the composer Alberto Williams, one of the founders of Argentine classical music. The arched span was not merely structural poetry; the curved underside was conceived as a soundproofed music room, a place where the grand piano could sit and the elder Williams could compose with the stream murmuring beneath the floor. Work began in 1943, built by two local firms, Sartora e hijos and Lemmi hermanos. The architect and his wife, Delfina Galvez Bunge - herself an architect - designed the spare interiors down to the doors, fixtures and boiserie, fashioning much of the furniture in a workshop set up on the site.

Look closely and the structure tells you exactly how it stands. A 9-by-27-meter weatherized concrete box - about 30 by 90 feet - rests its weight on the curved arch at its center and on bulkheads at either end. There are two front doors, one at each end of the bridge, opening onto stairways that run parallel to the curve and can be seen from outside through tall picture windows. The main glazing wraps the full perimeter, a window running 360 degrees around the house so the forest and the water are never out of view. Williams wanted something light, aerial and see-through, a structure that fused modern engineering with the topography rather than bulldozing it. It is impossible not to think of Frank Lloyd Wright's Fallingwater, finished a few years earlier over its Pennsylvania waterfall - but where Wright cantilevered terraces beside a cascade, Williams did something stranger and more daring: he bridged the water outright.

Here is the paradox at the heart of the house. Amancio Williams is one of the most revered figures in Argentine architecture, yet he built astonishingly little. His drawings overflowed with visionary schemes - suspended office blocks, a hall for spectacle, an airport floating over the River Plate - and most stayed on paper. The Bridge House is the great exception, the place where his ideas left the page and stood up over running water. That rarity is part of why it matters so much. Argentina's roll of modernist landmarks is short and precious: the Casa del Puente in Mar del Plata and, in nearby La Plata, the only house Le Corbusier ever built in South America, the Casa Curutchet. To lose the bridge would be to lose a large fraction of a nation's modernist inheritance - which is exactly what nearly happened.

Genius does not guarantee care. Declared a national historic monument in 1997, the house was nonetheless left without the money to maintain it, and it slid into abandonment - vandalized, stripped, and finally gutted by fire in September 2004. For years it stood as a blackened concrete skeleton over a stream, an icon at risk. The municipal government cleaned and secured the shell in 2005, and the long fight to save it began. A comprehensive state restoration followed, and on 20 April 2023 the fully restored Casa del Puente reopened as a museum. The recovery earned international honor: Italy's 2023 Gubbio Prize, and then, on 8 February 2024, the World Monuments Fund / Knoll Modernism Prize - confirming the standing of Williams's bridge among the masterworks of modern architecture, eight decades after he first imagined it.