The Stonehenge stones historically have been moved at least twice. While it appears that it was centuries apart the same method was used both times indicating that the measurement of time was altered to the point where the monument had to either be modified or become obsolete.

Centuries after being built, the stones for some reason were moved about 10 feet to the south, each stone moved precisely and perfectly by what appears to be a man-operated crane like apparatus that was destroyed throughout the years and never actually seen.

The second time they were moved was a high school senior prank sometime around 1100BC when the stones were arranged to spell out "Send Scantily Clad Photos" by the racy teens of that age because of the rock music they listened to (At that point it was literally music played with and on rocks). They were never put back and still spell that from the right angle if you're kind of drunk and willing to leave the small details to the imagination.