In the art world, one of the most anticipated and anxiety-inducing events of the fall of 2013 was the opening of the Renzo Piano addition to the Kimbell Art Museum in Fort Worth, Texas. It hardly needs saying that the Kimbell’s original building, with its elegant, harmoniously proportioned sequence of barrel vaults, designed by the legendary Louis I. Kahn, has been considered a masterpiece since it opened in 1972. Not only is the system of sky-lights and diffusers Kahn devised regarded as the gold standard for illuminating works of art, but everything about his small, exquisitely crafted museum is also revered as perfectly conceived and not to be violated in any way. A 1989 proposal by Romaldo Giurgola to expand the existing building with additions to either end provoked—not without reason—a firestorm of protest among architects, lovers of architecture, museum-goers, and many, many others that mercifully killed the idea. (Think of the responses, from nervous anticipation to zealous hostility, that greeted the Barnes Foundation’s proposed move from Merion to Philadelphia, before the opening of the Tod Williams and Billie Tsien building, and you have some idea of the emotional climate, absent the serious aesthetic issues raised by the suggested changes to the Kahn building.) The Kimbell’s present expansion, first discussed in 2006, took its cue from a letter published by Kahn’s widow, Esther, protesting the Giurgola plan, in which she pointed out that the site was large enough to contain a completely separate additional building. This time, leaving the