Contrary to popular belief, buildings move. And according to the new exhibit at the Guggenheim, “Frank Lloyd Wright’s Guggenheim Museum: Restoring a Masterpiece,” the museum has been moving quite a bit since it opened almost 50 years ago.

Wright’s plan for the museum was to create a monolithic spiral without joints. The ramps were formed of cast-in-place concrete, and most of the outer walls were made by spraying gunite — a mixture of cement and sand injected into an air stream in a hose and mixed with water just before being forced out of the nozzle — into a plywood framework reinforced with steel. This process allowed Wright to create the continuous curve of the exterior facades of the building. It did not, however, leave room for the expansion and contraction that buildings experience throughout their life spans.

The current exhibit includes photographs, drawings, computer-generated images, building materials, restoration devices, and interviews with members of the restoration team, city officials, and private sponsors of the project, all of which are mounted on a series of boards in the middle of the main ramp. While the restoration project itself has been comprehensive and methodical, the exhibit feels small and a bit rushed. It’s too bad, since the building provides so many opportunities to make the actual restoration part of what is on display. Why not provide a viewing platform where visitors can see an area of the building that is being repaired, or install webcams to show the work as it is happening? In an era that embraces restaurants with open kitchens and reality television, it seems the museum has missed an opportunity to engage visitors.

In 2004, the Guggenheim began a meticulous yearlong study of the building. The study revealed that cracks in the facade, which have plagued the Guggenheim since its opening, were not caused by structural instability but by subtle movements, most caused by thermal expansion. Concrete is particularly susceptible to temperature changes, and as environmental conditions change it is normal for it to expand and contract. Most concrete buildings today are designed with expansion joints to allow for this movement, but Wright’s monolithic spiral was not. As a result, when conditions shift, the facade walls develop tiny cracks to relieve the pressure caused by the expansion of the concrete.

The study involved attaching a series of monitors to the existing cracks in order to determine the direction and force of each movement. Radar and ultrasound were also used to map the location of steel reinforcements in the walls without further disturbing the integrity of the building. The restoration project also includes skylight and window replacement, application of a new exterior coating, reinforcement of the upper ramp walls, and the installation of a corrosion protection system. These improvements are less visible than the facade restoration; as a result, less space is devoted to them in the exhibit.

In September 2005, scaffolding was erected around the exterior of the building so that the restoration team could have complete access to every crack in the building’s surface as well as the skylight in the dome. Inside the museum, the uppermost portion of the ramp and top-floor galleries are closed so that work can be done on the structural reinforcement of that portion of the ramp. All aspects of the project are expected to be completed in 2008, with the exterior repainted and scaffolding removed in time for the 50th anniversary of the building.

Although the Guggenheim is often held up as one of the great Modernist buildings, Wright did not consider himself a Modernist. He was disenchanted with the cold, hard edges of modernism, often referring to his Midcentury Modernist peers as the “glass box boys.” Wright found his inspiration in the natural world and often adapted organic forms into his buildings. He believed that the spaces in buildings should be transcendental, lifting visitors up and reconnecting them to the natural world.

The Guggenheim design grew out of Wright’s long obsession with the spiral. For a museum, it was a brilliant shift. Rather than move people through room after room, often requiring them to retrace their steps, Wright’s plan carried everyone to the top of the building via elevator then allowed them to meander down the moderately sloped ramp at their own pace. The artwork became a part of the experience of moving through the building.

In many ways, the Guggenheim transformed the relationship between art and the museum. To visit museums used to be about seeing the objects within the building, but in Wright’s plan experiencing the building became just as important as experiencing the art. The Guggenheim paved the way for the modern museum where the building is as much of an attraction as the artwork.

Although today the building is widely celebrated, the Guggenheim caused a great deal of controversy in the years between the unveiling of its plans in 1943 and the opening of its doors in 1959. Most criticism during that period focused on the building’s audacity and unusual form. The art critic Hilton Kramer dismissively called it “an architecture which succeeds in having only one organic function: to call attention to itself.” Others described the building as a giant washing machine, and one critic simply called the architect Frank Lloyd Wrong. When the Guggenheim opened, reviews were mixed. While the art critic John Canaday declared it “a war between architecture and painting, in which both come out badly maimed,” the architect Philip Johnson praised it as “Mr. Wright’s greatest building, New York’s greatest building … one of the greatest rooms of the 20th century.”

Six months before Wright died in 1959, a picture was taken of him on the roof of the museum. He is standing in profile with a backdrop of scaffolding; only a sliver of the curvaceous facade peeks thorough. It is said to be the last time that Wright visited the building. He died at his home in Arizona before construction was completed.

Approaching the building today, buffed down to its original gray concrete and wrapped in scaffolding, a visitor realizes that this must have been similar to the last view that Wright had of his museum. The current exhibition about the restoration project, while interesting, is not the primary reason you should visit the Guggenheim right now. The real joy is the rare architectural opportunity of seeing this building in the same state as it was last seen by its architect.

Wright’s building is arguably one of the greatest pieces in the Guggenheim’s collection. As the museum competes for public attention by launching expansion projects all over the world, it is refreshing to see it also investing in the architectural treasure that it already has.