Of the many mysteries about Louis Kahn's life, one of the biggest is how he went from being a talented, if not particularly groundbreaking, modernist, to one of the greatest architects of the 20th century. For much of his career, Kahn labored in semi-obscurity in Philadelphia, often struggling to find steady employment. It wasn't until he was nearly 50 that things began to click, and he started designing the buildings that would redirect the course of architecture.

The glacial pace of Kahn's career formed a kind of sub-theme in My Architect, Nathaniel Kahn's 2003 film about coming to terms with his father as a parent and an architect. Kahn's messy life, which included children with three women, and its impact on his work, came more clearly into focus this spring with the publication of Wendy Lesser's The Life of Louis Kahn, the first comprehensive biography of the Philadelphia architect.

And now we have a museum exhibit to complete the story, with a huge array of artifacts. Louis Kahn: The Power of Architecture, which opens Friday at the Fabric Workshop, offers everything from Kahn's Central High yearbook to the hand-painted mural from his famous Trenton bathhouse project.

The real gold is in the crude cardboard models Kahn fashioned for projects like the Kimbell Art Museum in Fort Worth, Texas, and the Bangladesh parliament. Those architectural rough drafts are evidence of Kahn's many false starts and show him thinking through the designs of his greatest masterpieces, almost in real time. Kahn's best work fused a modern sensibility with the timelessness and heft of ancient monuments. The visible effort in the exhibit's models makes his genius all the more human and accessible.

The Fabric Workshop exhibition is not the first large show devoted to Kahn's work since he died of a heart attack in 1974 on his way home from a business trip to Bangladesh, but it is the first retrospective since My Architect catapulted Kahn back into the limelight, and it reflects the growing respect for his accomplishments. Organized by the Vitra Design Museum in Germany, the show offers an international take on his career, with a heavy emphasis on his big, marquee projects. Since debuting at the Vitra in 2013, the exhibit has traveled the globe, visiting nine cities. This is the last stop.

It's hard to believe, but its touchdown in Philadelphia almost didn't happen. Vitra had trouble finding a venue that could display the 200-plus objects included in the exhibit. Only after Marion Stroud, the Fabric Workshop's late founder, offered space at the museum, did the show find a home in Kahn's hometown. Ironically, most of the objects on display come from the University of Pennsylvania's Architectural Archives.

Born in Estonia in 1901, Kahn arrived in Philadelphia when he was 5, and his deep connection with the city is essential to understanding his work. He grew up poor in North Philadelphia in the shadow of its massive factory buildings but managed to gain entrance to Central High and the University of Pennsylvania, where he studied architecture under the renowned beaux arts classicist Paul Philippe Cret.

Even though he was classically trained, Kahn came of age during the heyday of modernism. He did stints in the Philadelphia offices of George Howe and Oscar Stonorov, whose work (PSFS building and Hopkinson House, respectively) was deeply influenced by Le Corbusier. Like them, Kahn enthusiastically embraced modernist ideals. His early designs, like West Philadelphia's Mill Creek housing project, adhered to Corbusier's functionalist, towers-in-a-park aesthetic.

One of the most interesting — and horrifying — pieces in the exhibit is a 1939 drawing showing Center City completely leveled from river to river, its rowhouses replaced by a dozen or so scattered, cruciform housing towers. Kahn made the sketch for the U.S. Housing Authority, and it was later displayed at the Museum of Modern Art in New York. His work for city planner Edmund Bacon and the 1947 Better Philadelphia Exhibition similarly reflected the modernist urge to clear-cut the city wholesale and start anew.

It's hard to believe Kahn's heart was in such schemes. As the show progresses, it becomes clear he harbored conflicting views about this approach to cities, which played out after World War II through urban renewal. An early television documentary shows him as a something of boulevardier, sauntering down Walnut Street in a jaunty suit and bow tie. Unlike his contemporaries, who continued to replicate generic, International Style designs, Kahn was deeply attuned to the specifics of place.

His feeling for cities in general, and Philadelphia in particular, come through in several wall quotes. "A city," Kahn declares in one excerpt, "is a place where a small boy, as he walks through it, may see something that will tell him what he wants to do with his life." This hardly sounds like a person who would level Center City.

The turning point for Kahn came in 1950, when he spent three months as a fellow at the American Academy in Rome. He used the trip to visit ancient sites in Greece and Italy. The show includes a selection of gorgeous Kodachrome snapshots of temples and amphitheaters taken by a traveling companion. But most revelatory are the evocative sketches Kahn made from memory, covering the pages of his notebook in thick layers of color. Looking at these primal, forceful forms, it's hard not to think of the monumental brick towers Kahn designed a few years later for the Richards Medical Labs at Penn. As his buildings took on the soulful grandeur of ancient temples, the architecture profession began to break away from its its emphasis on lightweight, placeless forms.

One weakness of the exhibit is that it tells Kahn's story thematically, rather than chronologically. The Fabric Workshop also was unable to accommodate the 6-foot-tall model of  City Tower, the faceted skyscraper Kahn wanted to build near City Hall.

Still, as you progress through the six themed sections, you can more or less piece together the story of Kahn's life and how his personal experiences impacted his architecture. Watching My Architect in advance would nevertheless be good preparation. The show doesn't dwell on Kahn's affairs with architects Anne Tyng and Harriet Pattison — a big part of the film — but it's easy to see from the drawings included in the show that they were influential in nudging Kahn toward his modern-ancient fusion.

It's striking how much talent coalesced in Philadelphia in the '60s. The show includes several fascinating models made by Robert Le Ricolai and August Komendant, the structural engineers who collaborated with Kahn as he explored the expressive power of concrete. The drawing that is sure to stop Kahn fans in their tracks is a sketch by Mexican architect Luis Barragán, suggesting the plan for Kahn's celebrated Salk Institute in California.

Unlike other paradigm-shifting 20th-century architects — Louis Sullivan, Frank Lloyd Wright, Le Corbusier, Robert Venturi — Kahn wasn't much of a writer. We are fortunate to have these objects to tell his compelling story, and to have them here in Philadelphia.

Louis Kahn: The Power of Architects runs Friday to Nov. 5 at the Fabric Workshop, 1214 Arch St., Philadelphia. See homepage for details of related events.