By Claire Marshall
BBC News, New Mexico
In the blazing July heat, thousands of people have made their way in to the parched New Mexico desert to visit the so-called "Trinity Site".
Today the Trinity site can still provoke raw emotion
A black lava-rock obelisk with a commemoration plaque marks the detonation site of the world's first nuclear bomb, exploded exactly 60 years ago.
Stan Hall was 20 years old when the Trinity test took place.
The day before he had worked all day at the foot of the steel tower from which the bomb was suspended, putting the final touches to equipment which would help to measure the blast.
Bad weather delayed the detonation, and it was not until just before dawn that he witnessed the explosion.
"I felt elated, because of a job well done," he told the BBC. "I knew that the war would soon be over."
The explosion had completely vaporised the steel tower Mr Hall had been working in the shadow of.
Now 80, he looked through his dark glasses at the tourists in t-shirts, trainers and baseball caps taking photos of each other, and then at the children squinting up at the monument.
"It was worth it," he said.
'Just doing my job'
"Sooner or later someone would have got this weapon. It ended up saving many lives, including Japanese lives."
I asked him how he felt about working on something that had changed the world.
His response was modest: "I didn't really think about it - I just had my job to do".
Some residents in the nearby town of Socorro still remember the day of the detonation.
Dave Wade was nine years old at the time.
"The blast shook all the windows out of the house," he said in a deep southern accent.
"My dad was looking out and he said that the sky turned a mint green. It stayed that way for maybe one or two minutes.
"We didn't know what was going on - it was very secret back in those days."
Younger locals are not sure what to make of the controversial legacy lying just down the road.
Michael Curry, in his twenties and also from Socorro, came to the Trinity site for the first time this year.
"I don't know whether to think 'wow, cool', or whether to think it's horrible to be praising this. It is history, though."
One eyewitness said it was as if someone had turned the sun on with a switch. Picture: Los Alamos National Laboratory
Some feel this is a tragic anniversary, arguing that the world has been living with the threat of annihilation ever since the Trinity test took place.
Shigeko Sasamori was 13 when the bomb exploded over her home city of Hiroshima.
She was severely burned on more than half her body, and her face had to be entirely reconstructed.
Shigeko came to New Mexico to campaign against nuclear arms.
Surrounded by peaceniks holding flowers and banners, she said: "The survivors are still suffering from leukaemia and other cancers.
"I am here to beg them not to build any more of such weapons, and to destroy the ones they have".