Redditor gumballbrain (Trapexoid on Tumblr) was messing around with a photo of the top of a fire hydrant one day when he noticed that the flaking paint and rust resembled a planet covered in water and solid land. Since then, he's made a hobby of taking photos of fire hydrants and finding the planets hiding on their lids.
gumballbrain manipulates the images in Photoshop, and says he enjoys the process of taking an ordinary urban object and imagining the worlds he uncovers—dreaming of the inhabitants, the societies, the politics that come out of these geographies. They remind me a bit of Christopher Jonassen's photos of the bottoms of cooking pots that look like distant planets. It's interesting to see that our pareidolia finding planets in ordinary objects.
The artist has posted more of these fire hydrant planets on Tumblr.