Beneath an ordinary elementary school in Washington DC is a stark reminder of a time when many Americans feared the apocalypse.
Barely touched for decades, a Cold War-era fallout shelter, equipped for a nuclear attack, now sits dormant and gathering dust in the basement of the Oyster-Adams school's cafeteria.
The walls of the 80-metre-long underground tunnel are lined with cardboard boxes, containing the remains of rations intended to feed more than 500 people for a fortnight.
Packs of stale — but apparently still edible — crackers are piled up near the narrow entrance, alongside large barrels of drinking water.
There are basic medical supplies, such as bandages and tongue depressors, as well as metal drums with removable rubber seats that would have served as portable toilets.
"This material was designed to sustain life," said Mike Washvill, a military veteran and volunteer at The Cold War Museum in Warrenton, Virginia.
"You had 700 calories per person per day, you had 1 litre of water per day for that two-week period — the most rudimentary of survival supplies.
Aside from silver air-conditioning ducts installed in recent years, the shelter was left untouched for nearly six decades, giving a rare glimpse into a bygone era when the US government and its citizens believed nuclear war was not only likely but imminent.
It is one of thousands of shelters established across the United States in the 1960s at the urging of former US President John F Kennedy.
Many were set up under apartments or office buildings and are now long buried and forgotten.
But as Russia holds out the threat of using nuclear weapons amid its invasion of Ukraine, the relationship between Washington and Moscow has reached a new breaking point.
And old anxieties are rising to the surface.
'Putin has raised the spectre of nuclear war'
In February, when Russian President Vladimir Putin officially declared war on Ukraine, his pre-recorded message contained an ominous warning some read as a nuclear threat.
"Whoever tries to interfere with us should know that Russia's response will be immediate and will lead you to such consequences that you have never experienced in your history," he warned.
Within days, he put Russia's nuclear forces on high alert, increasing its arsenal's readiness to launch.
The move was labelled a "totally unacceptable" escalation by the US and led to a flurry of anxious stockpiling not seen since former US president Donald Trump boasted he had a "much bigger and more powerful button" than North Korea's Kim Jong-un.
Nukepills, an American company that sells anti-radiation medication online, sold nearly 15 million potassium iodine tablets worldwide in roughly two weeks, according to CNN.
The European Union also encouraged its members to boost supplies of iodine pills and nuclear protective gear.
"President Putin has raised the spectre of nuclear war," said Nina Tannenwald, a senior lecturer in political science at Brown University who has written a book about nuclear deterrence.
"He's rattled the nuclear sabre a bit."
How real is Putin's threat?
Nuclear weapons have not been used in a war since the United States dropped bombs on Hiroshima and Nagasaki with devastating consequences in 1945.
In the decades since, it was hoped the concept of "mutually assured destruction" would prevent one nuclear-armed country from carrying out an attack on another.
But Dr Tannenwald said so-called "strategic" nuclear weapons, aimed at destroying entire cities, are not the only options Vladimir Putin could turn to.
Russia is also estimated to have around 2,000 lower-yield "tactical" nuclear weapons designed for more limited use on the battlefield.
"So, there's nothing small about these tactical nuclear weapons.
"But because they are less destructive than the really big nuclear weapons, there's a perception that they could be more usable.
"And that makes them more tempting to reach for in a crisis."
At present, hundreds of US satellites and spacecraft are monitoring Russia for any signs of further escalation but have not spotted anything of concern.
"We haven't seen anything that's made us adjust our posture, our nuclear posture," Jake Sullivan, the national security adviser to President Joe Biden, recently told reporters.
The US has repeatedly ruled out sending troops into Ukraine or enforcing a no-fly zone over the country, out of fear it would further escalate the risk of nuclear retaliation.
The fallout shelters Americans forgot
America's Cold War-era shelters were not designed to protect from the direct impact of a nuclear blast.
Instead, they are intended to shield from "fallout" — radioactive materials sent up into the atmosphere and then potentially carried long distances before falling back to earth.
"The 1960s, around the Cuban Missile Crisis, was basically the peak of people's concern about radioactive fallout and nuclear war," Mr Washvill said.
"There was a very big panic and a very big effort to try to improvise as many fallout shelters as possible."
The Office of Civil Defence produced videos explaining the science behind nuclear fallout and urging people to make plans for where they would take their families in an emergency.
Buildings with fallout shelters were marked with distinctive yellow signs like the ones still found at the elementary school in Washington.
"In the case of the school here, during the day, the primary occupants would have been the students," Mr Washvill said.
"After school hours, however, anyone from the neighbourhood might have come here to get to the building."
Back then, the US government and the public were fixated on the threat posed by the Soviet Union as the two superpowers came perilously close to nuclear conflict.
Today, there is another risk factor making some countries nervous.
Europe fears risk of nuclear accident
When Russian forces seized the Chernobyl nuclear power plant in the early stages of the recent invasion, Ukraine's President warned it could lead to another catastrophe at the site of the world's worst nuclear disaster.
While the UN nuclear watchdog has expressed concern about the situation, the International Atomic Energy Agency has said Chernobyl is unlikely to be an imminent safety threat to the world.
A greater concern would be if Ukraine's four operational, modern nuclear plants got caught up in the fighting.
But the memory of Chernobyl still looms large for many Europeans.
The accident in 1986 forced the evacuation of entire communities around the plant and is believed to have contaminated 200,000 square kilometres of Europe.
In Norway, where radiation from Chernobyl was still affecting livestock such as reindeer decades after the disaster, defence officials have reportedly advised citizens to "dust off" Cold War-era bunkers.
"If an accident happens, as with Chernobyl, we will all in western Europe be affected by that if the wind goes in this direction," Norway's Defence Minister Odd Roger Enoksen told the UK's The Times.
A number of European countries have also reported a spike in sales of iodine pills, which are used to block radioactive iodine from being absorbed by the thyroid gland.
Russian forces began withdrawing from Chernobyl in April but remain in control of the Zaporizhzhya facility, Europe's largest nuclear power plant.
Despite concerns raised by Ukraine and the International Atomic Energy Agency, Dr Tannenwald believed the risk of a nuclear accident remains low.
"Ukraine has a lot of nuclear power plants and the war isn't over yet," she said.
