The once-secret shelter built to house Congress after a nuclear attack will reopen to tourists after a two-year renovation, but the $15 million monument to the Cold War still has some secrets.

About 70 percent of the 112,000-square-foot bunker, deep under the posh Greenbrier resort, will become a secure repository for data and documents.

"It's being converted from people storage to data storage," said Linda Walls, manager of The Greenbrier's bunker tours.

That means the new tour route covers less ground than those that began in 1995, after the bunker was publicly exposed.

Still, there's be plenty to see in a facility the size of two football fields stacked atop one another, including a new exhibit hall and the first public display of two dozen historic photographs. Resort guests can begin touring on Monday, and the public can tour on Wednesdays and Sundays, beginning Aug. 20.

The bunker, a vast box protected by 5-foot-thick concrete walls and 18- to 25-ton blast doors, was built at the direction of President Eisenhower and completed in 1962, when the United States and the former Soviet Union were bracing for what appeared to be an inevitable nuclear war. The attacks never came, so the bunker was never used.

For 30 years, though, staff working undercover as television repairmen kept the bunker constantly ready to support 1,100 people, with everything from food to books, magazines and board games.

But the rows of narrow steel bunk beds were set up for efficiency, not comfort.

"This was not built to preserve individuals," Walls said. "This was built to preserve a democratic system of government."

Some 70 Greenbrier employees worked there on a need-to-know basis. Signs, several of which are now on display, blared such warnings as, "Share a Ride, Not Your Secrets" and "Keep It Under Your Hat ... The Enemy Has Ears."

There were working radio broadcast booths and a TV studio with two backdrops, the U.S. Capitol framed by fall leaves and the White House rimmed in spring flowers. Two theaters with plush green seats were to serve as chambers for the House and Senate.

Part of the site's appeal for Eisenhower, historians say, was that the resort and its owner, the railroad operator CSX Corp., had a long-standing relationship with the government. The Greenbrier once served as a 2,000-bed Army hospital and held diplomats from enemy nations after World War II.

Deep in the mountains, it was unlikely to become a target. And weather experts theorized that air flow patterns would clear fallout quickly.

Secrecy about the bunker was broken in 1992 when an article in The Washington Post Magazine argued that it was no longer viable.

The 90-minute tours cost $30 for adults and $15 for children, and all depart from the White Sulphur Springs Civic Center. Reservations are suggested, with groups limited to 30 people. Children under 10 are not allowed.

Tours will continue when the hotel closes for three months for a $50 million makeover beginning in January, Walls said.