When people visited the Moon, they left sizeable items behind. I know that taking picture of this from Earth is incredibly hard, but: Did someone try? And what pictures do we have?
From Earth, you can't. This is actually quite a common question, and was answered by Telescopes.com. To see the Lunar Rover, for instance, would require a 75m telescope, far larger than anything ever built! The shadow of the Lunar Decent Stage is a bit larger, but even that is quite difficult to achieve, requiring the perfect timing, although even then, it would barely be detectable, and not as definitive proof.
There are two additional things that do have some proof of the Lunar Landings having happened. The first is that the Lunar Reconnaissance Orbiter took pictures of the lunar lander sites from orbit, which you can see at the above link. The second is that 3 teams left a retro-reflector, known as the Lunar Laser Ranging Experiment on the surface of the Moon. These can be detected by special laser/ telescope pairs, and are quite distinct from areas without the retro-reflectors on the Moon.