The photo shows a railway disappearing into the distance, with yellow roses and red candles laid on the tracks at Auschwitz, the notorious Nazi death camp.
"Travelled to Auschwitz. Only photo I feel is respectful to post in Camp 2," says the caption.
The image, shared on Reddit, has caused an undercurrent of anger to bubble to the surface - not just about Auschwitz, but the sites of other atrocities around the world like the atomic bomb memorial in Hiroshima and Ground Zero in New York.
"The among of smiling, selfie-taking tourists was sickening," one user wrote about his trip to the Dachau concentration camp, in Germany.
"I saw a bunch of kids on the way out trying to do a bunch of stupid poses, silly faces and hand signs while trying to get the main entrance in the background (standing on the trail tracks) for photos. Had to repress the urge to smack them," said another.
One person said their visit to Dachau was punctuated by an annoying tourist who kept whistling the "mockingjay" tune from the Hunger Games movies.
"I don't understand how people feel that behaving in these ways could be at all acceptable."
Last month, a group of men was kicked out of Ground Zero in New York, for taking selfies with a blow-up sex doll during a bucks' party.
"I'm speechless. I don't even have any words for that - it's a disgrace," said Rosanne Hughes, whose husband was on the 107th floor when the plane hit.
"That is sacred ground, I lost my husband and I don't even know what to say - it's disgusting."
And while sex toys don't appear every day, many say tourists often lack respect.
"Seeing the tourists taking photos and smiling actually made me angry. Not annoyed.
Honestly angry. I almost said something, only thing stopping me was I felt like causing a scene would be worse," said one New York user.
"I understand it's not done in malice, I just couldn't imagine using a selfie stick with a group of friends, smiling and laughing where thousands of people were killed," agreed another, who works right next to the World Trade Center.
One tourist, who was visited New York with his family, says he opted out.
"We wound up for a pose while there not even thinking about it, and it suddenly hit me how wrong it was ... and I put the camera down," he said.
But while some tourists take photos without considering the context, many Reddit users argue it's a way of preserving the intense emotions they felt.
One user discussed the Peace Memorial Museum in Hiroshima, which has preserved bloodstained children's clothing from when the city was rocked by an atomic bomb.
"The descriptions for most of them said they managed to find their way back to their homes, only to succumb from their injuries in their parents arms. I couldn't hold back the tears."
Another said Auschwitz didn't feel real until they walked through the camp.
"Yeah I knew people suffered greatly, but I didn't have any frame of reference for what it might have been like until I saw it for myself. It really is indescribable, and no words do it justice."
In that sense, it's a way of making sure humans never let these things happen again.
Most Redditors agreed it all comes down to intention.
"It's not a tourism stop. It's a memorial. A solemn reminder of the horrors that man is capable, a promise to never repeat, and an opportunity to pay your respect," said one.
"Trying to use real human misery of others for your own benefit is gross," said another.
"Are you trying to trade genocide for internet points? Instagram likes? Facebook reactions?"
The user who posted the original photo admitted to "persistent lingering sadness".
"I posted this one specifically because it shows not just the location, but mainly captures unity of people's remembrance in the flowers and candles," they said. "That's why I felt it was respectful and justified to share, not because 'I' visited Auschwitz and wanted people to know."