Upon its completion in October 1958, the Union Tank Car Dome, located north of Baton Rouge, Louisiana, was the largest clear-span structure in the world. Based on the engineering principles of the visionary design scientist and philosopher Buckminster Fuller, this geodesic dome was, at 384 feet in diameter, the first large scale example of this building type. A Necessary Ruin chronicles the dome’s history via interviews with architects, engineers, preservationists, media, and artists; animated sequences demonstrating the operation of the facility; and hundreds of rare photographs and video segments taken during the dome’s construction, decline, and demolition.