There was a time when you could see the core structure of the twin towers.... In the early 1970s, New Yorkers witnessed a surreal sight: the skeletal cores of the World Trade Center towers piercing the skyline before their outer walls were completed. The image shows the “core structure” — the massive steel spine that housed elevators, stairwells, and utilities — bathed in the glow of a setting sun. Each tower’s core was a fortress of 47 steel columns, built to bear much of the building’s vertical load. Around it, a perimeter of 59 steel columns on each face created the towers’ distinctive facade. For a brief window during construction, the cores rose high above the city, exposed like the ribs of a colossal machine. Within just a few months, those skeletal frames would vanish behind aluminum cladding and glass, transforming into the iconic Twin Towers. But for those who saw them in this unfinished state, it was a rare glimpse of the engineering heart of what would become two of the most recognizable buildings in the world. #archaeohistories