The pillars shown in this illustration belong to gates called torii. According to Wikipedia, "The custom to donate a torii started to spread since the Edo period (1603 – 1868) to get a wish to become true or to thank for a wish that became true." You can read more about them here: https://en.wikipedia.org/wiki/Fushimi_Inari-taisha

Each gate in the image was built on a different day, but I have only annotated the clearest, most prominent of them.