In a key scene during the moving first-person documentary My Architect, director Nathaniel Kahn interviews his mother, a landscape architect who worked with his late father, architectural giant Louis I. Kahn, and was the last of his two mistresses. As the illegitimate son who knew his father only through brief, vivid childhood encounters, Nathaniel wonders whether his mother's affair was worth the heartache of raising him by herself, playing second fiddle to Kahn's wife, and growing old alone. Though clearly stung by Kahn's inaccessibility and deceit, she answers, "Yes, it was worth it"–not so much because of the greatness of the affair itself, but because she was too stimulated by their working relationship to measure the emotional costs. As the younger Kahn's absorbing, thoughtful personal journey progresses, his role as the bruised son sifting through the wreckage left by his absentee dad starts to recede, even though the pain doesn't seem to go away entirely. Touring his father's magnificent structures, Nathaniel shows signs of coming around to his mother's point of view, and of realizing that Kahn's towering contributions to art and humanity perhaps exceed (if not altogether excuse) his shortcomings as a father, a husband, and a lover. It says something that both of Kahn's mistresses and their illegitimate children attended his funeral service in 1974, even though they were shunned in the back row, their presence fervently opposed by Kahn's steadfast wife Esther. Found dead in a Penn Station bathroom, alone and more than half a million dollars in debt, Kahn didn't live to see the completion of his most magnificent achievement, the Capital Complex of Bangladesh, which took 23 years to construct. Nathaniel saves that stop for the end of the tour, when its impact is most overwhelming. He spends the preceding time visiting Kahn's other buildings and chatting with colleagues, rivals, lovers, and his two half-sisters. Considered by many to be the most important post-war American architect, Kahn built imposing structures (including the Salk Institute, the Exeter Library, and the Kimbell Art Museum) composed of concrete, brick, and steel, with an emphasis on geometric shapes that invite natural light. But his stubborn aesthetic convictions resulted in far more unrealized projects than masterpieces, particularly when he lost the chance to rebuild his native Philadelphia in the late '50s and early '60s. (An interview with his architectural nemesis Edward Bacon, who was in charge of the project, shows that the rancor between them lives on.) My Architect may strike some as a narcissistic endeavor from the start, like one man's gooey, pop-psychological therapy sessions inflicted on helpless movie audiences. Yet as Nathaniel Kahn considers his father's buildings, they seem less like monuments to an absent dad than gifts to the world, spaces crafted with a unique sensitivity to the spiritual. All regrets aside, the director clearly feels a swell of pride in telling strangers, "My father built this."