The diamond grid is not an ornamental facing: it holds up the building, along with a central core. “Diagrid construction” is a little more common today, but still fairly unusual; perhaps the most famous or notorious example of it is the Gherkin in London. This was a very early example. It was finished in 1964, and although it was originally built for IBM, it fits its current owner very well: its steel grid is a good demonstration of what steelworkers are capable of. The architects were the New Orleans firm of Curtis and Davis.
