The scientist led the way past cabinets packed with samurai armor, drawers of bird's nests, racks of African blankets and shelves of stuffed alligators until, at last, he reached a metal door.

With a wry smile, he pressed his badge against its electronic lock and ushered his visitor into a cavernous warehouse. Glistening in the muted light were jars upon jars upon jars of specimens of every conceivable species -- giant Venezuelan rats, diaphanous jellyfish, pale cactus flowers -- all carefully labeled and suspended for posterity in an alcoholic mixture that suffused the room with a pungent smell.

"This," announced James Pecor, "is Pod Three."

From the outside, the Smithsonian Museum Support Center could easily be mistaken for one of the many federal bureaucracies with outposts in Suitland. The Smithsonian center -- an enormous concrete building of nearly the same bland hue as the nearby Census Bureau, Washington National Records Center and National Oceanic and Atmospheric Administration offices -- occupies a grassy, 41/2-acre lot across from a strip mall of storefronts including Sterling Dental Center, Crystal Nails and Lord's House of Glory.

But to walk through the Smithsonian's primary off-site storage facility, on Silver Hill Road, is to enter a world out of some fevered imagination. Round one corner and you are facing drawer after drawer of slides containing seemingly every type of flea. Round another and you are peering into a carbon dioxide-cooled steel and glass case housing rocks from outer space.

Then there is Pod Three -- known as "the wet pod," said Pecor, who helps maintain the U.S. government's mosquito collection there. But equally vast and entrancing is Pod Four, where such oversize items as petrified tree trunks and Buddha statues and totem poles are kept on enormous yellow and blue shelving. (Picture Indiana Jones's attic as organized by Ikea.)

Perhaps you have lain awake at night wondering whatever happened to the skulls of elephants that President Theodore Roosevelt brought back from safari, or to Sitting Bull's hand-drawn auto-picto-biography, or to the cashmere shawl given to President Martin Van Buren by the government of Oman. Now you can rest easy in the knowledge that they are all being lovingly cared for in Suitland -- along with roughly 30 million other artifacts, documents and specimens.

And that's only counting items from the National Museum of Natural History, which keeps about one-fourth of its collection at the Suitland site, according to the center's director, Elizabeth Dietrich. There are also tens of thousands of items belonging to the National Museum of American History, the Smithsonian American Art Museum, the -- well, you get the idea.

"By the time we're done giving a tour, some people are turned to jelly," said Deborah Hull-Walski, manager of the anthropology collection.

Not that the center is open to all comers. If the string of museums along the Mall is the Smithsonian's public showcase, then the Suitland facility is more like its private storeroom -- a place to restore and preserve everything there is no room, or no reason, to exhibit.

Even many longtime residents of Suitland are unaware of the treasures hidden in plain sight there. For the past several years, Sylvia Quinton, founder of Suitland Development Corp., has been negotiating with some of the federal institutions that have offices in Suitland to form a partnership to educate local youth. But Quinton said she had not thought to contact the Smithsonian. "I know that they're out here, but I guess I don't really know what they do," she said.

Still, technically, every item maintained at the center is the property of American taxpayers -- which means it must be made available to anyone who can give a good reason for wanting to see it. Generally, that means scientists and other researchers and the occasional student group. But increasingly, now that the National Museum of the American Indian -- dedicated last week on the Mall -- has opened a separate, architecturally striking Cultural Center on the same Suitland property, Native Americans are coming to view artifacts in the Support Center's collection.

Prospective visitors must contact the museum whose collection they want to see and schedule an appointment at the center, which does not charge admission.

Of Global Renown

Smithsonian officials said they do not track the number of visitors to the Support Center. But the assortment of researchers working in Suitland on a recent afternoon gave a sense of the variety. In the anthropology library, two women from France pored over photographs of Native Americans. One floor up, in the entomology section, Rampa Rattanarithikul had come from Thailand to look at slides of mosquito larvae under a microscope. She is putting together an illustrated key to mosquito species in Thailand -- an important tool to combating malaria there. "In my country," she said, "we do not have a place with all the specimens. But they are all here."

Meanwhile, just outside the Support Center, in a hangar that is part of a separate Smithsonian complex known as the Paul E. Garber Facility, Peter Adam, a graduate student from UCLA was carefully measuring a whale bone. Once the domain of the National Air and Space Museum, which has moved most of its planes to a new site in Northern Virginia, the Garber facility houses several Support Center collections, including not just modern whale bones, but also fossilized ones.

Adam said he hoped the information he gains from today's species can be used to extrapolate the size of prehistoric ones. It might be unknown to the rest of the world, but to whale researchers, Suitland is famous, Adam added. "I came here to do my master's work as well," he said. "You just don't see this kind of setup anywhere else."

The needs of such researchers as Adam add a twist to the mission of those who manage the Suitland collections. On one hand, their job is nothing less than to, as Dietrich put it, halt the forces of decay. ("Well," she acknowledged, "eventually everything returns to dust. But still . . . ") That means minimizing an object's exposure to anything that will degrade it -- humidity, high temperatures, sunlight, pests, pesticides, the oils on a human hand.

On the other hand, the items at Suitland must be easily accessible. At times, the collections managers seem to take as much pride in the ingenious methods they have devised to solve this challenge as they do in the objects themselves. Notice, said Charles Potter, who maintains the whale bones, how they've been mounted on the same type of mobile, vertical metal frames used to store small planes. See, said the paleobiology collections manager, Jann W.M. Thompson, how these fiberglass jackets we've created for our dinosaur fossils allow you to view them from all angles without ever touching them.

Sensitive Guardians

Since the Support Center opened in 1983, it has become a recognized leader in the field of collections management, visited by about 20 groups of managers from other museums in the past year, Dietrich said.

Taped to some of the anthropology collection's sleek metal storage cabinets are photographs to remind visitors of a different era, when the Smithsonian's overflowing collection was crammed in stairwells or unused restrooms, or thrown into boxes like odds and ends on sale in a dusty antique shop.

These days, collections managers are not only more sophisticated, but also more culturally sensitive. Tribal representatives are consulted about the proper housing of objects from their heritage. Care is taken never to place profane objects over the head of sacred Buddha sculptures, for instance.

Native peoples who come through the center seem to appreciate the effort, managers at the center said. On a recent tour, one American Indian was moved to donate the hat he was wearing -- a baseball cap bearing the words "Choctaw Veteran" -- on the spot.

A few days later, the hat sat on a table in the anthropology department, awaiting classification. Hull-Walski reached for it to show it off, then stopped short with a guilty smile.

"You know, I really should put on gloves to handle this," she said.

David Rosenthal, assistant collections manager for the Smithsonian Museum Support Center, displays a huge stone head from the Olmec culture. Preserved rare and extinct birds, including a sharp-tailed grouse and heath hens, are among the millions of artifacts, documents and specimens at the Support Center, located on 41/2 acres in Suitland.James P. Dean, head of the center's bird collection, shows the Montezuma Oropendola and the intricately woven nest it prepares for its young.