A not-so-undisclosed location in Fla.

Magazines displayed backyard do-it-yourself versions. Castro Convertibles pitched its foldaway “jet beds’’ as bunker-ready. And a pair of publicity-savvy newlyweds actually spent their honeymoon inside one for 14 days.

President Kennedy, who was facing a series of nail-biting face-offs with the Soviets, even recommended a fallout shelter for all Americans “as rapidly as possible’’ in an October 1961 speech. Two months later, Kennedy was presented with his own top-secret tropical bomb shelter off Palm Beach, Fla., on an inlet of the Atlantic Ocean.

Few even know it is here, but some area residents believe the bunker is a must-see attraction that could put Peanut Island, a manmade islet, on the map.

Termed the “Detachment Hotel’’ in documents, the fallout shelter here was built by Navy Seabees in less than two weeks at the end of December 1961 and sits a short stroll from a rambling colonial-style house that doubled as a US Coast Guard station. Deftly camouflaged by trees, it was hard to spot. If people asked, they would be told it was a munitions depot, nothing more. Kennedy visited the bunker twice during a drill.

“The government never declared it existed until 1974,’’ said Anthony Miller, a member of the executive board of the Palm Beach Maritime Museum, a nonprofit organization that leases part of the land on Peanut Island and runs a charter school and gives tours of the bunker and the former Coast Guard station. “But it was the worst-kept secret in Palm Beach.’’

With the Soviets intent on shipping nuclear warheads to nearby Cuba, Kennedy was assured a radiation-proof haven a mere 5-minute helicopter hop from his oceanfront winter home on millionaire’s row in Palm Beach. Peanut Island sits just between Palm Beach and its ritzy companion, Singer Island. It was intended to be used as a terminal for shipping peanut oil; that never happened, but the name stuck.

To ensure the president’s safety during the summer, when he visited the Kennedy compound in Hyannis Port, a sister shelter was built on Nantucket Island in 1961; it has never been open to the public.

The Florida bunker, which fell into disrepair in the 1990s, was cleaned up and has been open for tours since 1999, shortly after the museum leased the land. Buried under layers of concrete and built with quarter-inch-thick walls of steel and lead, the bunker looks like something from the television show “Lost.’’

Inside, to the left of a long corrugated tunnel, lies the decontamination shower, the first hint that the possibility of a nuclear showdown was not thought to be far-fetched. Eleven months after the shelter was built, the Cuban Missile Crisis erupted.

The shelter is decorated as it was then, more or less, with replica pieces and a presidential seal. The decor is fittingly rustic, a far cry from Jacqueline Kennedy’s sensibilities. There is room enough to hold 30 people on 15 metal bunk beds for 30 days. A Taylor Transmitter ham radio sits on a desk in a corner.

“His mobile phone, back in the day,’’ Miller said.

Shelves are stocked with giant tins of waterless hand cleaner (today’s Purell), cans lined with lead that contained drinking water (no longer advisable), deodorant to clean clothes, petroleum jelly, castor oil, and ample Army K-rations. Gas masks sat at the ready. An escape hatch lies at one end, just in case the Russians were coming.

In one corner, there is a rocking chair, a nod to Kennedy’s bad back.

But just how long the museum can keep operating the bunker is another matter. The museum has been running at a loss for years now, Miller said, and the curators are embroiled in a decade-long tussle with a few Palm Beach County commissioners to open a full-service restaurant, as many museums do, to help them foot the bill. A proposal will be put forward again soon to the commission, although some of its members are leery about whether the restaurant plans to serve liquor. They are concerned for security on an island with no police force at the ready.

There are signs of detente, however, and Miller is hopeful.

Priscilla Taylor, a county commissioner who said she was open to a restaurant if concerns were addressed, said the issue might be reconsidered.

“It’s a beautiful facility,’’ Taylor said. “The bunker has a story to tell, and they should be included in anything we do to promote tourism for the island.’’