In 2006, a group of inspectors from the New York City Department of Transportation were on their usual rounds of bridge and tunnel inspections. The rounds were usual except for one discovery: Somewhere deep in the Manhattan anchorage of the Brooklyn Bridge they stumbled into a hidden room filled with blankets, water, a shock-prevention drug called dextran, and 350,000 crackers.

Judging from the dates stamped on the supplies (1957 and 1962), what they discovered seemed to be a Cold War-era bunker or fallout shelter. Emergency survival shelters weren’t unusual back then – you can still see thousands of old “Fallout Shelter” signs and logos on buildings throughout the city. But one inside the Brooklyn Bridge? That no one knew about? That’s a different story.

The inventory of the bunker’s cache followed a typical shopping list for emergency preparedness during the arms race of the 1950s and 60s: barrels of potable water (which the labels say can double as commodes when empty, so there’s that), first aid supplies and blankets, boxes of high-calorie survival crackers (yum), and a healthy supply of the drug dextran, which is used to prevent and treat shock (probably a good idea if you’re stranded inside a Brooklyn Bridge bunker).

The supplies were marked as coming from the Office of Civil Defense, the Cold War precursor to what eventually became FEMA. Since the DOT had no idea the stash was there – or why it would be there – explanations are really only guesses. And, as with all the rooms and tunnels inside the anchorages of the Bridge, the public isn’t allowed inside. So the question of where, exactly, in the Manhattan-side anchorage they found the room, the DOT is keeping that under wraps for security reasons.

They found one other stockpile alongside the survival supplies – a bunch of Mad Men-looking New York City promotional posters. The bunker may have been closed to the public, but not to a little old fashioned public relations.