Hyperboloid

The year was 1956. Plans to demolish Penn Station hadn't yet been set into motion. But plans to demolish NYC's other famous train station were well underway. When Grand Central was constructed in 1913, its architects envisioned that it would one day be the base of a skyscraper, but in the early 1950s, developers hoped to demolish the terminal altogether to make way for what would have been the tallest building in the world. Famed architect I.M Pei was tasked with the job, and he designed an 80-story, hourglass-shaped, futuristic tower known as the Hyperboloid.
More details and a video on the never-built project