Suberiishi (“Sliding Rock”) Jinja (I think that’s the name, but I haven’t heard it pronounced and I can’t find a reading for the kanji on the website — it could be “Kasseki”) is one of the minor jinja associated with Kinkasan Koganëyama Jinja, the jinja on a sacred island in Miyagi Prefecture that I visit every year. The spring issue of the jinja newsletter has an article about it.
This jinja is a little way up the mountain, behind the main sanctuaries and beside a small river. There used to be a small sanctuary on a stone platform with a torii in front of it. The building was far too small to enter, but that is not uncommon for sanctuary buildings, particularly for subsidiary jinja.
However, last March there was a large earthquake off the coast of Fukushima (I believe it was an aftershock of the Great East Japan Earthquake), and the shaking on Kinkasan (which is the name of the island) was very strong. This shook a large boulder loose and sent it sliding down the slope, straight into the jinja’s sanctuary, destroying it. The boulder then stopped on the platform, exactly where the sanctuary had been.
When the priests saw this, they all said, “That’s a real sliding rock”, and so the decision was taken not to move the rock or rebuild the sanctuary. Instead, the event was taken as a sign of the will of the kami, and the rock itself was designated the goshintai (the sacred object housing the kami). A shimënawa was wrapped around it, and on January 28th this year a matsuri was held to mark the enshrinement of the kami in the rock.
There is a photograph in the newsletter. The rock, with a shimënawa around it, is sitting on the stone platform, at the top of a short flight of steps, beyond a red torii. In this case, I really can’t argue with the decision to take it as a sign from the kami.
Edit: DerekL points out in the comments that Google Maps has a photo.