One of the great what-ifs of architectural history is on view at the Italian Cultural Institute in Westwood: a congress center that Louis Kahn designed as a tensile bridge spanning a canal in the Arsenale of Venice. Had it been realized, it might have rivaled the Kimball Museum, the Salk Institute, and the Parliament of Dhaka among his masterworks. But the client was Venice, a museum city dedicated to mass tourism, which prefers mediocre replicas to inspired originals. Kahn died in 1974 before his design was completed, and it joins the Frank Lloyd Wright palazzo of 1953, and Le Corbusier’s hospital of 1964, as one of the lost opportunities for La Serenissima to infuse the old with the best of the new. Only now, with Calatrava’s footbridge across from the station, and David Chipperfield’s extension to the San Michele Cemetery have the Venetian authorities begun, haltingly, to address the present day.