4. There Was Supposed to Be a Roof Garden
The original plan for Carnegie Hall was to have a roof garden, all the rage during that time with fabulous entertainment venues atop Madison Square Garden, the Hotel Astor and many more locations. It never happened, but in the most recent renovation, a rooftop space was added while protecting the original roof. According to Richard Malenka, three new roofs were built (one to protect the original roof, one temporary for additional protection during construction, and the new roof deck).