Gravel crunched under the tires as our guide stopped the government SUV near a section of train bridge. No trains have ever crossed the bridge — it stands alone in the middle of the desolate Nevada desert where it was built to study the effects of atmospheric nuclear detonations.

On May 8, 1950 a 27-kiloton nuclear blast shifted the steel girders of the bridge several feet to the side where they remain a rusted testament to the tremendous power of nuclear weapons.

In the surrounding playa are other ruins. There's an 8-by-8-foot, reinforced bank vault with concrete blown off the front. The steel supports, blown back by a 37-kiloton blast on June 24, 1957, look like hair in the wind.

There are 50-foot concrete domes smashed like egg shells, aluminium structures crunched like cans, even typical American two-story homes that were exposed to the raw power of nuclear blasts.

Welcome to the Nevada Test Site, about 60 miles north of Las Vegas. All these sights are included on the free tour offered monthly by Bechtel Nevada, the civilian contractor that runs the site.

Of the 1,051 nuclear tests the United States has performed, 928 were done at the site giving it a lunar, crater-pocked surface. The largest blast hole is the highlight of the public tour. Sedan Crater is 1,280-foot wide pit formed in 1962. The Atomic Energy
Commission used a 104-kiloton thermonuclear device to explore the possibility of using nuclear blasts for excavation.

"It worked great but we don't do it today because of all the contamination left behind," said tour guide La Tomya Glass. She wears a thermal luminescent dosimeter badge to monitor exposure to radioactive contamination.

She'll meet tour groups at the Las Vegas office for a briefing before they are bussed with their sack lunches up to the town of Mercury at the site entrance. Mercury, a company town complete with steakhouse and recreation center, is not usually open to the public.

During the peak activity in the 1980s, 50 buses converged at Mercury each morning — bringing test site employees from Vegas and Pahrump. Now about 10 arrive each day.

One of the first things folks see on the tour is the collection of splintered benches once used by scientists, politicians and VIPs to watch the blinding white blasts and mushroom clouds of early tests. From 1951 to 1962 observers in goggles looked down at tests on Frenchman Flat — now home to the rusting train trestle and bank vault.
Parked aircraft and military vehicles were also subjected to tests — as were some 1,200 pigs. The swine, bred for the military, were clothed in various fabrics to test their response to the heat generated by nuclear explosions.

Farther up the Mercury Highway tour groups pass — but do not approach —the Device Assembly Facility (DAF). The complex cost $100 million to design and build and $10 million to maintain annually.

It was never used for its intended mission. Former President George Bush signed the nuclear test moratorium before it was completed, putting an end to critical nuclear testing before the facility was ready. It was designed to confine an accidental blast with a collapsing gravel roof. The facility is still used for "stewardship" of the nation's stockpile of nuclear devices, according to DAF Deputy Manager Dennis J. Kelly.

"This is the best place to do that type of work safely," he said.

On the hill above it is the area marked on maps as "CP" — Control Point.
From this ridgeline testers looked down on Frenchman Flat and another area used for testing, Yucca Flat.

One building at CP features a room where testers watched a wall of 15 TV screens, wind-speed monitors and a geophone showing ground movement. During the era of regular testing, a public relations person would do live radio broadcasts from the room offering a countdown for the public.

Near Yucca Flats is area U1a, the site of current testing. Scientists from Los Alamos and Lawrence Livermore test plutonium in tunnels 960 feet underground.

Complex manager Richard Ziegenbein said testing the nation's nuclear devices is like testing old cars left in a parking lot for 20 years.

"We need to know if these bombs will still work," he said.

In order to stay within the limits of the test-ban treaty, current testing is "sub-critical" meaning no fission takes place.

A test called "Piano" was performed by Lawrence Livermore in September while another called "Armando" conducted by Los Alamos is in the works now.

The Nevada Test Site is also home to a radioactive waste landfill. The test site is divided up into 30 numbered areas with areas 3 and 5 used to store radioactive waste. About 27 million cubic feet of waste have been buried in sealed containers so far, according to Low Level Waste Operations Manger Doug Clark. From October 1-27, 177 shipments brought 200,000 cubic feet to the site from around the country. More than $80 million in contaminated gold from dismantled reactors is buried on the site. It's all well sealed in a very arid, remote area, Clark said.

"We haven't had a release since the first waste arrived back in 1965."

The War on Terrorism has added another chapter to the long, complicated history of the Nevada Test Site.

Bechtel Nevada employees have trained about 3,000 first responders in Weapons of
Mass Destruction preparedness each year since the attacks of 9-11, Glass said. The training is focused on how to deal with radioactive contamination. Homeland Security Director Tom Ridge visited the site with officials from the Federal Emergency Management Agency two years ago.

Security at the site has also increased, with Bechtel trucks patrolling the site's perimeter 24 hours a day, seven days a week.

From nuclear-powered rockets tested for use in beating the Russians to Mars to the testing for a National Nuclear Waste Repository at Yucca Mountain, there’s a lot still going on at the Nevada Test Site. The best way to learn more about the site, which has an annual budget of about $600 million, is to sign up for a free tour. Test site tours are usually offered once a month, though there will be no tours offered for December or January.

"They fill up quickly," said Glass.