Introducing Curbed SF's newest series Curbed's Could Have Been, where we investigate some of the most outlandish and grandiose proposals that were never built. Know of a plan that never saw the light of day? The tipline's always open or you can leave a comment after the jump.

Proposal for five-block parking garage [Photo: SAN FRANCISCO HISTORY CENTER, SAN FRANCISCO PUBLIC LIBRARY]

Back in 1947 the city was dealing with a major influx of traffic and parking constraints, so what better way to deal with it than proposing a five-block-long, nine-story garage that could hold 15,000 cars? Bound by Minna, Natoma, Third, and Eighth Streets, the proposal came from the City's architect and would be accessed by overpass linkages to roads. The plan included ground floor retail with eight floors of parking - not to mention a helicopter landing field on the roof. Why not? Today the site is a mix of the Moscone Center, SFMOMA, and many blocks of office and apartment buildings.

The same five blocks today (click to enlarge) [Photo: Bing Maps]