In June 1943, Frank Lloyd Wright received a letter from Hilla Rebay, the art advisor to Solomon R. Guggenheim, asking the architect to design a new building to house Guggenheim's four-year-old Museum of Non-Objective Painting. The project evolved into a complex struggle pitting the architect against his clients, city officials, the art world, and public opinion. Both Guggenheim and Wright would die before the building's 1959 completion. The resultant achievement, the Solomon R. Guggenheim Museum, testifies not only to Wright's architectural genius, but to the adventurous spirit that characterized its founders. Wright made no secret of his disenchantment with Guggenheim's choice of New York for his museum: "I can think of several more desirable places in the world to build his great museum," Wright wrote in 1949 to Arthur Holden, "but we will have to try New York." To Wright, the city was overbuilt, overpopulated, and lacked architectural merit. Still, he proceeded with his client's wishes, considering locations on 36th Street, 54th Street, and Park Avenue (all in Manhattan), as well as in the Riverdale section of the Bronx, before settling on the present site on Fifth Avenue between 88th and 89th Streets. Its proximity to Central Park was key; as close to nature as one gets in New York, the park afforded relief from the noise and congestion of the city. Nature not only provided the museum with a respite from New York's distractions but also leant it inspiration. The Guggenheim Museum is an embodiment of Wright's attempts to render the inherent plasticity of organic forms in architecture. His inverted ziggurat (a stepped or winding pyramidal temple of Babylonian origin) dispensed with the conventional approach to museum design, which led visitors through a series of interconnected rooms and forced them to retrace their steps when exiting. Instead, Wright whisked people to the top of the building via elevator, and led them downward at a leisurely pace on the gentle slope of a continuous ramp. The galleries were divided like the membranes in citrus fruit, with self-contained yet interdependent sections. The open rotunda afforded viewers the unique possibility of seeing several bays of work on different levels simultaneously. The spiral design recalled a nautilus shell, with continuous spaces flowing freely one into another. Even as it embraced nature, Wright's design also expresses his unique take on modernist architecture's rigid geometry. The building is a symphony of triangles, ovals, arcs, circles, and squares. Forms echo one another throughout: oval-shaped columns, for example, reiterate the geometry of the fountain and the stairwell of the Thannhauser Building. Circularity is the leitmotif, from the rotunda to the inlaid design of the terrazzo floors. The meticulous vision took decades to be fulfilled. Originally, the large rotunda was to be accompanied by a small rotunda and a tower. The small rotunda (or monitor building, as Wright called it) was intended to house apartments for Rebay and Guggenheim but instead became offices and miscellaneous storage space. In 1965, the second floor of the building was renovated to display the museum's growing permanent collection, and with the restoration of the museum in 1990–92, it was turned over entirely to exhibition space and rechristened the Thannhauser Building in honor of one of the most important bequests to the museum. Wright's original plan for the tower—artists' studios and apartments—went unrealized, largely for financial reasons. As part of the restoration, a 1968 office/art-storage annex (designed by Wright's son-in-law William Wesley Peters) was replaced by the current structure, designed by Gwathmey Siegel and Associates Architects, LLC. This tower provides four additional exhibition galleries and, some thirty-five years after the initiation of construction, completed Wright's concept for the museum. In 2001, the Sackler Center for Arts Education opened to the public. Located just below the rotunda, this 8,200-square-foot education facility includes the Peter B. Lewis Theater, part of Frank Lloyd Wright's original architectural design for the building. Some people, especially artists, criticized Wright for creating a museum environment that might overpower the art inside. "On the contrary," he wrote, "it was to make the building and the painting an uninterrupted, beautiful symphony such as never existed in the World of Art before." In conquering the static regularity of geometric design and combining it with the plasticity of nature, Wright produced a vibrant building whose architecture is as refreshing now as it was 40 years ago. The Solomon R. Guggenheim Museum is arguably Wright's most eloquent presentation and certainly the most important building of his late career. —Matthew Drutt