Tractors crawl out of a hole in the ground, hauling rubble to the surface. A coat of choking dust filters through a cage of scaffolding in the marble Rotunda.

But a glimpse of the genteel past peaks out from underneath layers of cream, teal and rose paint in the House of Representatives' lounge. With fiberglass dropped ceilings and false walls and floors stripped out, the original olive-green silk wall covering still hangs - a bit tattered, but a clue to the finer trappings of the seat of state government when it first opened 90 years ago.

Surrounded by the demolition incidental to shoring up the building to withstand an earthquake, a squad of "history detectives" is painstakingly picking away at the remnants of decades of well-meaning but slapdash repairs, cover-ups and technology upgrades. Their interest is more than academic - focusing on the goal of restoring the building to its former splendor.

"We're really lucky," says Carice Pingenot. "Fundamentally, [past Capitol workers] were really lazy. When they remodeled, they didn't take anything down."

So crews ripping out fluorescent lights and sheetrock found ornate milk-glass light fixtures and plaster cornices - along with a mummified rat, old newspapers, whiskey bottles and several pairs of leather shoes, worse for the wear.

Finished in 1915 at a cost of $2.7 million, Utah's Capitol has aged gracefully, but not well. The prospect of a moderate earthquake threatens to shake the building 48 inches back and forth. And the air-conditioning ducts, aluminum windows and once-trendy paint have obscured the building's historic integrity. Gutting the Capitol to shore it up provided a convenient opportunity to restore a more authentic interior.

The eye candy of the $212 million Capitol restoration is secondary to its structural support. But when the building reopens in 2007, the earthquake-proof base isolators under the basement and the steel beams in the rotunda will be hidden from view. Paint, plaster and artwork will be the public face of the building. The two simultaneous preservation efforts - structural and aesthetic - complement each other.

"Base isolation minimizes the loss of the historic fabric of the building," says Burtch Beall, the architect who managed the restoration and seismic improvements of the Salt Lake City-County Building in the 1980s. "The Capitol represents a period of growth and development. There's a character there that we no longer are able to produce."

Figuring out what the building looked like back then is part sleuthing, part interior design. Historic preservation specialists with Capitol Restoration Group - three architecture firms collaborating on the restoration - have gathered photographs, letters and newspaper articles to decipher the decoration. They've climbed around the building on scaffolding and ladders, rubbing away layer after layer of paint and cutting out chunks of plasterwork for microscopic inspection. Each of 5,500 painted limestone panels plastered on the walls and columns of the first floor were numbered, mapped and stored in a warehouse for eventual remounting.

Because Utah's Capitol design was the result of a turn-of-the-century competition, workers have found numerous photographs and drawings of the building. But the laziness of those long-ago workers, new technology and the relative youth of Utah's Capitol also aid the investigation.

"Your building has been well cared for," says Bob Loversidge, CEO of Ohio-based Skulley Caldwell Architects, one of the restoration partners. "It's been modified. Significant character has been lost in some areas. But it's been respected and well-maintained. It's pretty intact compared to some other buildings we look at."

Contractors from New York to Denver will interpret what Utah workers find, rebuilding $10,000 light fixtures and reproducing wall silks. About $27 million has been set aside for finishing the interior of the building.

Decorative painters will painstakingly replicate ornate stenciling and pinstriping Pingenot stripped and traced to find shades of ochre and sage in the attorney general's office, governor's board room and old Supreme Court.

Murals inside the building - including a cyclorama of murals hung in 1934 as a Works Progress Administration project - have been covered with acid-free plastic sheets and foam core. Humidity and temperature meters transmit numbers to construction trailers 24 hours a day. Workers still are trying to determine whether a half-inch wide outline of black paint on the murals was original or added later.

The 200 free-hanging paintings, portraits and sculptures that grace the Capitol's halls and rotunda - the so-called "Alice Collection," named for Alice Merrill Horne, the first woman elected to the state Legislature - have been catalogued and stored in a warehouse. One by one, they will be sent to Denver for conservation.

All the artwork will be cleaned and restored. When the building is opened, the collection will be more closely monitored and maintained.

"It will be managed like a historic site, rather than just a building that has been allowed to just kind of put things up willy-nilly," says Judith McConkie, Capitol curator.

In addition to surface changes, a few historic structural features will be restored. A glass floor underneath the rotunda will replace terrazzo installed in the 1930s or 1940s. And a granite terrace and elliptical walkway planned by original architect Richard Kletting finally will be built around the sides and front of the building.

Some things have been lost or will be difficult to replicate or replace. Fixing broken granite on the building's exterior is a dicey prospect because the Little Cottonwood Canyon quarry is closed. State leaders are negotiating with The Church of Jesus Christ of Latter-day Saints to dip into the church's cache of stone. Many of the limestone blocks on the first floor broke as they were removed, forcing crews to replace them with plaster. And with each successive renovation, workers took light fixtures home.

"They're probably hanging in someone's living room," says David Hart, Capitol Preservation director. "There is some stuff that has been done that is irreversible. The key is to reverse what we can. We're going back to what was originally constructed - to the best of our ability."

Despite the popularity of do-it-yourself interior design shows and the PBS series "This Old House," the Capitol preservationists are braced for some resistance from workers and politicians - particularly to the darker, earth-tone colors.

Longtime House Clerk Carole Peterson worries the building will revert back to a tan shade that covered everything when she first started working at the Capitol 30 years ago. She liked the pink-and-green House Chambers, circa a 1995-96 restoration, that others have panned.

"It was so drab in here," Peterson says. "When it's drab, you get depressed. The tan was depressing to me."

But State Historic Preservation Officer Wilson Martin believes Utahns will approve when the building reopens. He is consulted on each preservation decision and wholeheartedly endorses the project.

"We're on the verge of being able to have a Capitol building that shows the strengths and vitalities of our state," Martin says. "This building will show we respect our history. We respect our traditions. We value our heritage."