I recently came across this proposal, and it honestly fascinates me.
Skyscraper Bridges? — The Gotham Center for New York City History
Skyscraper Bridges? By Sam Lubell and Greg Goldin
www.gothamcenter.org
It was proposed by Raymond Hood, a well known architect in New York and elsewhere at the time (1920s). In his mind it would have increased density without unduly increasing traffic, as one of the main drivers of his idea was to combat the rising congestion (I have my doubts as to whether this would actually work, but the bridges would have to already be built to get a definitive answer...)
Architecturally, it was definitely feasible, and Hood hoped to build at least a dozen. Could we have seen tens, even hundreds of thousands of citizens living suspended over the water? Or was this just a pipe dream that could never realistically have come to fruition?
Quotes;
"Not to embrace this opportunity is to neglect the very pick of metropolitan locations."
"Land has often been reclaimed from water for purposes of habitation and agriculture. What is so extraordinary about creating land over water?"