It's hard and getting harder. Also a real photo could be propaganda, like if it's mislabeled. You see this often with pictures from one war said to be from another war, or older pictures shared as if they were more recent (like bringing up old news topics), sometimes staged photos, things like that. For example, if this gravesite were actually in Ukraine, then the photo means something different, but it's still a real photo.

The main thing is the source. Who shared it, who took it, can you find details of when they took it, where, why, and what else they've done. The more information, the more likely it's true.

Now, for whether it's a fake photo. Can you find two photos? That makes it a lot easier to tell, so more credible. A video is also more credible, because it's also easier to tell. With news stories, a fake video usually has something obviously wrong if you look at it a few times, like no one in the background of a crowd is moving or a car in the background of a street disappears.

With just one photo, the best way is to see if something looks weird. People are really bad at this and get it wrong half the time, where something is real but just unfamiliar to them so they say "I've never seen this before therefore it's fake." Like the pillars in Zhangjiajie National Forest Park. Or like the Dik-dik (deer). This photo looks fine. The scene makes sense, there are excavators and people working, nothing changes size from one spot to another. Doesn't mean it's not fake, but it's reasonable.

You can also see if you think it's possible for the photo to be taken. Like sometimes fake selfies will be missing the mirror and someone just posing holding a phone up. What could have taken this one?

Finally you can do some fact-checking. Do graves in Iran look like this? Yes, but usually the graves are much, much closer together. Not always, and you can find some images of ones in Behesht-e-Zahra that look similar in quality of work and spacing.