When an astonishing Gigapan image shot atop the Freedom Tower at One World Trade Center hit the Internet recently, few probably realized the massive undertaking that was required to capture this suddenly iconic image.  

In a remarkable making-of video Time's Senior Editor of Photo & Interactive, Jonathan D. Woods explains how the partnership between Time and Gigapan started with sketches on bar napkins and soon grew into a multi-state engineering challenge focused on capturing a panoramic image despite the physical and meteorological challenges present at the top of the building's spire. 

He also explains how the image took its inspiration from a famous photograph by Joe McNally that featured a worker at dusk changing the light bulb on the Empire State Building while the Twin Towers stood in the background. 

The effort to create the image could have been all for naught, as Woods explained that the team’s first real-world test atop a bridge in Portland failed to capture any images. 

Luckily the bugs were worked out of the system in time for the scheduled shoot and the crews took to the spire — a climb that induces vertigo even from watching the video — in favorable weather and captured what is likely to remain for some time as the most detailed photograph from the top of One World Trade Center. 

Over the course of five hours a Canon 5D Mark II with 100mm lens captured 567 photos that were stitched together to produce the final image. 

Time's "The Top of America" site includes a look at the ironworkers (many of whom are the children of those that constructed the Twin Towers) and includes a documentary on their efforts and more background on the meaning and emotions behind the contraction of the Freedom Tower. 

See the image and read the full story on Time.com.