A bunker under Launch Complex 39-A built for the Apollo era. Image source: SpaceFlightNow.com.
SpaceFlightNow.com posted an article November 19 about the bunkers built in the bottom of the two launch pads at Launch Complex 39 that were to be used if the Saturn V rocket blew up.
Picture the mighty Saturn 5 moon rocket, fueled and poised for blastoff from the Florida spaceport. But something goes wrong and everyone at the seaside complex must evacuate to safety. The answer that designers created for men to survive a detonating rocket was this protective cocoon built under the sloping northwest corner of both twin pads at Complex 39.
For the astronauts or crew support personnel at the top of the rocket, they would rely on a high-speed descent elevator to reach the base of the mobile platform. They join technicians working on the platform to jump down a chute on the north-side of the platform that connected to the teflon-lined slide that rapidly gets them underground.
That 200-foot slide empties into the aptly-named "rubber room" with its rubber floors meant to absorb the impact of the explosion occurring on the pad surface 40 feet above them. Hopping off the landing ramp, the people would scurry to their left into the fallout shelter, a domed room suspended on shock-dampening springs and sealed off with massive blast-proof doors. Inside, the chamber held 20 chairs, a toilet and carbon dioxide scrubbing equipment to keep the occupants alive until rescue teams arrive.
Click the above link to see more photos and read the article. One for the history books.