The skyscrapers along Park Avenue in the 40's and lower 50's are all minor engineering marvels. They're built atop the rail yard for Grand Central Terminal (an early adopter of the modern real estate concept of "air rights"). Many of the newer buildings are much taller than was anticipated when the terminal was constructed more than a century ago. This heavily constrains their foundations and anchor points, leading to unusual load-bearing designs such as the steelwork shown in the photo.