Joel Levinson was in his second year of architecture studies at the University of Pennsylvania when he overheard two students speaking as if they were up to no good. These being fellow building buffs, however, their illicit conversation turned out to be a far cry from planning house parties while perched in the library stacks. Instead, the whispered dialogue was more of the drafting table variety: “They were talking about attaching triangular shapes into their otherwise orthogonal, blocky building designs,” Levinson recalls. At the time, Levinson was intrigued. But today, he credits the moment with catalyzing his lifelong interest in what he refers to as “diagonality,” or put more simply, the study of diagonal lines.

Not long after that chance encounter, Levinson started to noticed diagonal shapes and vectors were just about everywhere he looked—from the magazines to which he subscribed to the work of his professors (who included Louis Kahn and Robert Venturi ). Of course, diagonal lines weren’t exactly invented when Levinson was a student during the 1960s. But they did perhaps experience a new wave of popularity within the visual zeitgeist. Since then, Levinson has continued to clock their occurrences over the decades, while balancing his own career and architectural practice. Many clippings, a few works of writing, and a website later, Levinson decided to take things to the next level and turn his massive archive into an online museum.

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That effort, which recently launched, is officially being billed as the Daring Diagonal Virtual Museum . But despite its digital format, the online venture includes an imaginary museum floor plan of its own. It’s through that portal that visitors can click into separate “galleries,” all of which are organized by either disciplines and themes or by chronology. There are sections devoted to architecture (unsurprising), fine arts, landscape design, interior design, and more—as well as troves of images that hail from ancient Egypt, the Computer Age, and numerous historic periods in between.

Through Levinson’s portal, interested users will find photographs of city-set skyscrapers such as the Hearst Tower and works by legendary artists including Frank Stella. There are also diagonal line-laden images that lie somewhere in between—examples of fine art that happen to show architectural works, as well as artistic renderings of humanity’s herculean construction efforts during various periods of progress. “What I hear from everyone is, first of all, they have trouble even pronouncing the word diagonality. But then I get a call back and they say, ‘Wait, I see it everywhere,’” Levinson says. “People have been blind to this very pervasive geometric technique.”

A Frank Stella piece included in the Daring Diagonal Virtual Museum.

An artistic rendering that unites multiple areas of Levinson’s focus.