LOS ANGELES » Before they face traffic on the 405 freeway, grab an In-N-Out burger or zip off to Rodeo Drive to see whatever they think is there, visitors who arrive here through LAX first stare up at the futuristic spider-shaped building at the center of the airport, welcoming them to the edge of America.

The structure, the Theme Building at Los Angeles International Airport, is one of the most famous emblems of this city, right up there with palm trees, surfers and the Hollywood sign.

For the last three years, it was shrouded in scaffolding after a 1,000-pound chunk fell off one of the upper stucco-covered arches and landed on the roof of a restaurant. No one was injured, but the need for serious renovation was highlighted.

As the building was being repaired, and retrofitted to better withstand earthquakes, it served as a disorienting eyesore, rather than a welcoming icon.

Its completion was delayed several times, to the consternation of airport officials.

But now the $12.3-million project is nearly done—all but some roof treatments and a few coats of paint—and it will soon be back to its former glory, only with earthquake protection.

Maintaining the Theme Building's midcentury flying-saucer shape while correcting for significant flaws in the design that threatened its structural integrity was a major challenge for architects, engineers and contractors.

Rather than reinforcing the building with lots of new concrete, which would be expensive and change its physical features, the designers built a 1.2 million-pound steel weight that sits on flexible bearings—known as a tuned mass damper. It anchors the existing roof of the central cylinder of the building and essentially serves to counteract the movement of the structure in an earthquake.

“;This is a more elegant way to go,”; said Nato Flores, president of Tower General Contractors, which ran the project. “;Because it doesn't affect the architecture the way that reinforcing it would have done.”;

The Theme Building, designed by the futuristic architects William Pereira, Charles Luckman Associates, Welton Becket & Associates and Paul Williams, was built in 1961 to serve as the center of the airport, a ticketing spot through which all passengers would pass.

But as a result of the manner in which LAX developed—highly decentralized without a single point of orientation, much like the city it serves—that plan never came together. However, the building's other features, like the observation desk—where people could watch planes take off and land and peer through the mini-telescopes—still attracted visitors. (The deck was closed to the public after the Sept. 11, 2001, terrorist attacks, but airport officials are contemplating a way to make it accessible again to visitors, possibly by appointment.)

The building's modern design and references to air and space travel came to stand for a new Western city on the edge of greatness.

“;From a historical point of view,”; said Paul Danna, president of the Los Angeles chapter of the American Institute of Architects,”;the building really symbolized the forward-looking spirit that Los Angeles had in the '50s and '60s and hope that Angelenos of that generation held for the future.”;

In 1997, the Encounter, a totally round restaurant, was opened in the building, with interiors and retro lighting created by Walt Disney designers, and it has remained a trendy drink spot.

After the chunk of building fell onto the Encounter in March 2007, the restaurant was closed for eight months, while the Theme Building was dressed for renovation and its flaws were attacked.

The center of the 135-foot-high arches, for instance, had inadvertently allowed condensation to collect on the steel supporting the plaster around them. The architect Gin Wong Associates addressed that by having the air outflow from the restaurant—once directed outside—piped through the arches as a continual drying system. The arches themselves were reinforced with new steel and flexible polymer-based plaster.

A screen wall that surrounds the building—a disaster waiting to happen, according to Jaime Garza, a project manager for Miyamoto International, the earthquake engineers behind the renovation—was reinforced at the top with carbon fiber.

By far the biggest feat was the tuned damper, 22 layers consisting of six two-inch steel plates each, and each layer ranging from 8,000 to 11,000 pounds, lined up with 164 bolts through the plates on top of the existing center cylinder of the building to absorb shocks.

“;It was a challenging project,”; said Flores, the Tower General Contractors president.

Cranes had to squeeze in under the arches. Oh, and the restaurant had to remain open the entire time, or the contractors would face a daily $5,000 penalty for any day it was closed.

Bringing the building back to full visual life is a matter of much excitement for those who care about urban history of Los Angeles, a growing interest among lawmakers, residents and preservationists in the last decade.

“;The word 'icon' can be overused,”; said Linda Dishman, the executive director of the Los Angeles Conservancy. “;But this building truly is. Anyone who enters or leaves here is greeted by the Theme Building. The city knew they had a treasure, and it preserved it.”;