The Citigroup Center, originally known as the Citicorp Center and now officially called 601 Lexington Avenue, is one of the most distinctive skyscrapers in Midtown Manhattan and one of New York City’s great stories of architecture and structural engineering.

In this episode, we explore how architect Hugh Stubbins and structural engineer William LeMessurier designed the 59-story tower around an unusual constraint: St. Peter’s Lutheran Church had to remain on the site. The solution produced the building’s famous elevated structure, enormous supporting columns, diagonal bracing and unmistakable 45-degree roof.

But shortly after Citicorp Center opened in 1977, LeMessurier discovered that a combination of quartering winds and changes made during construction could create a serious structural vulnerability. What followed became one of the most famous engineering ethics stories in modern architecture.

We trace the Citigroup Center from its 1970s design and construction through the structural crisis, secret reinforcement work, tuned mass damper, and its eventual place among the most recognizable landmarks of the New York skyline.

A story of skyscrapers, architecture, engineering, risk and responsibility in the heart of Manhattan.